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Dictionary of the History of Ideas

Studies of Selected Pivotal Ideas
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The idea of a Chain of Being, or Scale of Creatures,
is one of the guiding threads of interpretation of the
universe worked out in Western science and philoso-
phy. Like all ideas developed through a process of
elaboration lasting centuries, it can be defined only by
retracing its historical development in all its varied and
often contradictory complexity. It will suffice to point
out here what is constant in its many changing formu-
lations. The Chain of Being is the idea of the organic
constitution of the universe as a series of links or gra-
dations ordered in a hierarchy of creatures, from the
lowest and most insignificant to the highest, indeed to
the ens perfectissimum which, uncreated, is yet its
culmination and the end to which all creation tends.

This idea entails, as we shall see in the sequel, a
series of essential component ideas in the history of
Western metaphysics—the principles of gradation, of
plenitude or fullness, and continuity, along with the
principle of sufficient reason—and also defines man's
place in the cosmos with psychological and moral, and
sometimes even political, implications of fundamental
importance for intellectual history.


1. The Ontological Basis for the Gradation of Ex-
isting Things.
Historically we may trace the concep-
tion of a Chain of Being to the Platonic Idea of Ideas,
or Idea of the Good, discussed in the seventh book of
the Republic. This Idea is in fact the summit of the
hierarchy of knowable things, for not only do they owe
to it the quality of their being knowable, but derive
from it their very, existence by participating in various
degrees in its nature (509b). Thus, the supreme Idea
provides the logical basis of a world of sensibilia con-
ceived as graded with respect to perfection. The Idea
of the Good, however, is no more than a logical foun-
dation, insofar as no active element or agent intervenes
yet; instead, this element of activity is made an intrinsic
feature of the Demiurge, introduced by Plato in the
Timaeus. The Demiurge creates the sensible world
modelled on the intelligible one (27d-29c). He cannot
fail to generate things in that way since, being with-
out jealousy, his very nature is to desire that all things
approach as closely as possible to himself (29d-30a).
Fecundity is thus an essential element of divine per-
fection. Self-sufficient perfection is at the same time
self-transcendence in the sensible world. Thus God
becomes at once the logical and ontological foundation
of the world's multiplicity and variety.

This quality of generative self-transcendence of the
supreme Being finds its most radical expression in
Plotinus. It is of the very nature of the One in its
perfection to “overflow,” producing in its exuberance
the “other” (Enneads V, 21). All beings, then, partici-
pate in the nature of the Good in such measure as they
may, according to their individual capacity.

2. The Chain of Being as a “plenum formarum” or
Plenitude of Forms.
It is again in the Timaeus that we
must seek the source of what Lovejoy has called the
“principle of plenitude”: the idea that in passing from
the eternal order to the temporal, from the ideal to
the sensible, there must be realized a fullness of forms
in which every possible form becomes actual. If crea-
tivity is essential to the very perfection of the supreme
Being, existence cannot be begrudged any manner of
things, whatever their grade of perfection. Moreover,
the supreme Being creates after the likeness of an
intelligible model: for every idea there must be a
corresponding perceptible object; every possibility will
have its corresponding reality.

It follows—and Plotinus draws this consequence in
all its import—that the divine self-transcendence, or
inexhaustible power of the One, must in its creative
necessity reach the extreme limits of the possible.
There is a kind of chain of delegated productive
powers: every hypostasis in this generative scale is
involved in this productive necessity, and its creativity
must proceed out of itself to the extreme limit of the
possible. Nothing may be barred from existence, which
is to say, from more or less participation in the nature
of the Good (Enneads IV, 8, 6).


What is full obviously cannot admit any discon-
tinuity. Thus in the Chain of Being the principle of
continuity is associated with the principle of fullness
and is often confused with the latter. Aristotle had
already observed that in the world of living things the
different orders overlap. In the classification of animals
according to habitat—terrestrial animals, animals in-
habiting air and water—there are many intermediate
forms irreducible to one or another of these classes.
The passage from the inanimate to the animate is so
gradual that continuity makes the boundary between
the two orders imperceptible. It is the same for the
passage from the order of plants to that of animals,
so that for many living forms it is hard to establish
to which of the two classes they belong (Aristotle,
History of Animals VII. 1. 588b).

It is easy to see that such considerations should have
reinforced the principle of plenitude—even though this
was not authorized by the Aristotelian teaching on
potentiality and actuality, according to which there
do exist possibilities which have not yet come into
existence (Metaphysics III. 1003e 2; XII. 1071b 13).


1. The Principle of Plenitude and Christian Theol-
The idea of an inexhaustible divine productivity
which cannot but create all possible forms, thus estab-
lishing a full and continuous chain of existing things,
was transmitted to Christian philosophy from Neo-
Platonism, chiefly through the medium of Augustine
and the Pseudo-Dionysius. And it gave rise immedi-
ately to a series of antinomies at the heart of Christian
thought. The first of these (in order of importance) was
the question of reconciling this divine self-transcen-
dence, this constitutional inability not to create every
possible thing without exception, with the divine at-
tribute of liberty.

The problem is clearly presented, for example, by
Abelard (Intro. ad theologiam, III). The Good can
produce nothing but good; to imagine there are good
things He might create, but does not, can only be to
imagine a jealous and unjust God. Thus goodness be-
comes a necessary divine attribute, limiting His free-
dom: being good, He could not have failed to produce
the world, nor could He have produced a better one
than the one He did produce. To the objection that
God acts, then, out of necessity rather than free choice,
Abelard answers that a certain necessity is inherent
in His nature. His goodness is so great that He does
spontaneously what it is impossible for Him not to do.
The “Spinozism” of this position has been clearly
pointed out by Arthur O. Lovejoy ([1936], pp. 71-72);
the connection between this problem and the theodicy
of Leibniz is no less evident.

Thomas Aquinas had to face the same problem, once
having accepted the principle of plenitude. God wills
the multiplicity of things inasmuch as He wills His own
essence and perfection, which indeed contains in itself
all things (Summa contra gentiles I, 75). And yet it
cannot be said that He acts out of necessity—and here
Thomas introduces the notion of consistency: the divine
choice is such that He chooses that which is consistent
with His perfection without, however, His being con-
strained by it (ibid., I, 81). But now it is clear that
this idea of the contingency of creation, which depends
on the divine choice, contradicts the principle of plen-
itude previously affirmed (ibid., II, 45; III, 71; Summa
I, q. 25, a. 6).

It is not surprising, given these difficulties, that the
official teaching of the Church tended to silence the
Platonic conception of a self-transcendent deity com-
pelled to create all possibilities. In general the “Chris-
tianization” of the Platonic doctrine of participation
involved a denial of emanationism, for the quality of
liberty had to be attributed to the Creator; and the
multiplicity of the forms of being flowing from the free
act of creation reflected, but did not modify or condi-
tion the richness and perfection of the Divine Being.

But if the idea of fullness, which requires the coinci-
dence of the possible and the real, involved Christian
thought in the difficulties we have seen, the application
of the idea of the biological continuum went far more
smoothly: it was in fact used repeatedly in praise of
that interconnectedness of things (connexio rerum) by
which nature passes only by steps from one kind to
another. The notion of continuity was amply used even
in psychology. In the nature of man different grades
of being meet: as microcosm, he recapitulates the
continuity of orders inherent in the scale of nature.
He is a workshop of all created beings (creaturarum
omnium officina
), and also stands as the union of all
creatures (medietas atque adunatio omnium creatur-
). Not independent of any creatures (nullius crea-
turae expers
), in common with the angels he has intelli-
gence, with animals he shares sensibility, with plants
the vegetable life, and with stones simple being. These
are recurrent motifs in, e.g., Albert the Great, John
Scotus Erigena, William of Conches; and also in
Thomas Aquinas, who places in the human soul the
boundary between corporeal and incorporeal things
(Summa contra gentiles II, 68).

2. Gradation in Nature and in the Sciences, (“scala
naturae” and “scala scientiarum”
). If the ascending
way is placed before the Christian as an itinerary of
moral edification, the same way is also, until the Ren-
aissance, the route that science must follow in recon-
structing that universal plan expressed precisely in the
Chain of Being. This methodical ideal of an upward


orientation is very evident, for example, in Raymond
Lully's (or Lull) construction of the tree of knowl-
edge—hence it was transmitted, thanks to the con-
tinuity of tradition set by Lully, to Renaissance ency-
clopedism, and to the pansophic ideal of the first half
of the seventeenth century.

“The likenesses to the divine nature,” writes Lully
in his Compendium artis..., (in Opera, Mainz,
[1721-24], III, 74), “are imprinted upon every creature
according to that creature's receptive capacities,
greater or less in each case... thus every creature
carries, more or less, the sign of its Maker.” Whence
the ideal of a way of knowing that proceeds by signs
(per vestigias) towards the reconstruction of the scale
of beings, of the hierarchies of the cosmos: from stone
to plant, to animal, to man, to the heavens, to the
angels, to God (cf. Liber de ascensu et descensu intel-
[1304]). Whence also, the full construction of
the “trees” of an encyclopedic knowledge that com-
prehends, in one organic picture of the universe, not
only sensible nature but also the ethico-political life
of man, the structure of the heavens, the divine hier-
archies, all the way to the arbor divinalis, which is
the culmination of the cosmic hierarchy. All things are
contained in Lully's sixteen trees; and in them, taken
together, we have another example of the continuity
of the Scale of Being—for every tree participates in
the nature of all the preceding ones, so that each is
a kind of compendium of the natures below it, and
contiguity is established between preceding and suc-
ceeding orders.

This ideal of knowledge as an ascent through the
grades of perfection of creatures is kept alive, and is
even renewed, through all of the Renaissance. For
example, Giordano Bruno, in the De umbris (1582), says
that all things have an orderly and connected structure,
and for that reason man should keep this scale of nature
clearly before his eyes, and make the effort to climb
from multiplicity to unity. It is this ideal that animates
all Renaissance encyclopedism, and is still quite alive
at the birth of the new science—as the ideal of a
reconstruction of the universe that shall exhibit the
qualities of comprehensiveness, gradation, and conti-
nuity—alongside the experimental method and its col-
lection of more or less unconnected and scattered
scraps of information. The program of the Royal Soci-
ety, for example, as formulated in 1669 by Thomas
Sprat (History of the Royal Society, p. 110), is witness
to this symbiosis of the techniques of experimental
research and the idea of a full and hierarchical uni-
verse. It is precisely the task of science to retrace the
steps of this universe: the program proposed “to follow
all the links of this chain [of the diverse orders of
creatures], till all their secrets are open to our minds.
...” The pages of the Philosophical Transactions are
a body of minute experimental data, offered to the
attention of men of science for no more than what
they are worth as disparate experimental findings; and
yet, for example, the various universal language plans
drawn up by certain eminent members of the Society
(John Wilkins being among the most notable) are based
precisely on the notion of a hierarchical classification
that holds good both ontologically and logically—for
nature as well as for science.


1. The Principle of Plenitude and the Plurality of
According to Lovejoy ([1936], Ch. IV), the
Renaissance idea of a plurality of inhabited worlds in
a physical universe infinite in space owes more to the
persisting force of the principle of plenitude than to
the new Copernican astronomy. The doctrine of an
infinity of worlds, as put forward most notably by
Giordano Bruno, is associated with his interest in the
new astronomy; but it is equally true that this doctrine,
as well as the hypothesis that there is life on these
worlds, could not be deduced from astronomical data
alone. The argument of which Bruno avails himself is
clearly a development of the principle of plenitude.
We may not think that a finite effect comes from an
infinite cause; in God, and therefore in the temporal
order that derives from Him, the possible and the real
coincide. Divine power cannot remain idle, divine
goodness cannot but be infinitely diffused, being infi-
nitely communicable. God, then, is a fertile father
(padre fecondo), endowed with an illimitable genera-
tive capacity (capacissimo di innumerevoli mondi),
as found in De l'infinito universo e mondi (1584),
Dial. I.

Descartes' authority, in the course of the seventeenth
century, lends support to this rejection of the idea of
the universe as a finite and self-contained sphere; and
the idea of a plurality of inhabited worlds is given great
currency in Fontenelle's Entretiens sur la pluralité des

2. The Full Universe of Leibniz. The diffusion of
the idea of a Chain of Being in eighteenth-century
thought was certainly and decisively aided by the
success of Leibniz, a great advocate of the principle
of plenitude and continuity, which he posited as a
correlative of the principle of sufficient reason. Leib-
niz, in one of his letters to Samuel Clarke (1715-16),

The least corpuscle is actually subdivided infinitely, and
contains a world of other creatures, of which the universe
would be deprived, if that corpuscle were an atom, that
is, a body of one entire piece without subdivision. In like
manner, to say that there is a vacuum in nature would be


to attribute to God a most imperfect production; it would
be to violate the great principle of the necessity of a suffi-
cient reason...

(Leibniz Selections, p. 236).

And elsewhere (De synthesi et analysi universali) the
principle of sufficient reason, whence flows, among
other things, the fullness of the universe, is defined as
one of the greatest and most fertile truths of human
cognition, since it assures us that all truths, even the
most contingent, have an a priori proof, i.e., a reason
for which they are rather than are not. This bond had
already been established by Leibniz in the Elementa
philosophiae arcanae
(1676): the principle of the har-
mony of things requires that there exist the greatest
possible quantity of essence. There is no gap among
forms; it is not possible to find an empty space or time.
Every particle of matter contains infinite creatures (cf.
also the so-called First Truths, Primae veritates [1686]).

The argument is drawn out at length in two other
writings of Leibniz: De rerum originatione radicali
(1697) and the Principes de la nature et de la grâce
(1718, posthumous). “Not only in no one of the singular
things”—writes Leibniz in the first of these, “but nei-
ther in the whole aggregate and series of things, can
one find a sufficient reason for their existence (nam
non tantum in nullo singulorum, sed nec in toto aggre-
gato serieque rerum inveniri potest sufficiens ratio ex-
). The world's reasons must therefore be sought
in something extra-worldly, different from the succes-
sion of states, or series of things, the aggregate of which
constitutes the world (rationes igitur mundi in aliquo
extra-mundano, differente a catena statuum, seu serie
rerum, quarum aggregatum mundum constituit
).” We
must go back, then, from the physical necessity of
things to their metaphysical necessity—which would
be precisely their sufficient reason. Leibniz goes on:

In possible things, or in their very possibility or essence,
there is an exigency to exist, or (so to speak) claim to exist;
in a word,... essence of itself tends towards existence.
Whence it follows that all possible things... tend with
equal right towards existence in proportion to their quantity
of essence or reality, or according to the grade of perfection
they contain; for perfection is nothing but the quantity of

Thus, given only that there is a reason for the passage
from possibility to actuality, it will follow that a maxi-
mum of reality will be actualized. In other words every
possibility has an “impulsion (conatus) to be real”; and
the sole restriction in the passage from the possible
to the actual is that imposed by the criterion of “com-
possibility,” the reciprocal compatibility of possi-
bilities. From the conflict of all the possibilities which
severally seek existence, the result will be the existence
of the maximal series of all possibilities.

The argument is taken up again in the Principes,
in relation to the problem of the monads. All is full
in nature; every monad is a living mirror that reflects
the universe; and there is an infinity of degrees in
monads, les unes dominant plus ou moins sur les autres
(ibid., pp. 3-4). The sufficient reason for the existence
of the universe cannot reside in the series of contingent
things, but only in God, from whose perfection it
follows that from the impulse towards existence proper
to all essences, the most perfect of possible worlds will
result. Without that we should be unable to say why
things are, and why they are as they are (ibid., pp.

3. Ethico-political Consequences of the Idea of the
Chain of Being in the Eighteenth Century.
It is Leib-
niz, as we know, who draws from the idea of a Chain
of Being, and particularly from the principle of pleni-
tude, those optimistic consequences already implicit—
consequences which for that matter did not escape
others before him, for example, Giordano Bruno (cf.
De immenso [1591], II, 13). Already in the De rerum
originatione radicali
(1697), Leibniz passes from the
principle of sufficient reason to the perfection of the

... from what has been said it follows that the world is
most perfect, not only physically, or, if one prefers, meta-
physically, because that series of things has been produced
in which there is actually a maximum of reality, but also
that it is most perfect morally.... The world is not only
the most admirable mechanism but insofar as it is composed
of souls, it is also the best republic, through which the
greatest measure of happiness and joy is conferred upon
these souls, in which their physical perfection consists

(Leibniz Selections, p. 351).

Experience seems to show the opposite: particularly
if we consider the conduct of mankind, the world seems
rather chaotic than ordered by a supreme wisdom. But,
objects Leibniz, it is not fair to judge the whole by
the part. We know only a small part of an eternity
infinitely extended, namely the extent of the memory
of a few millennia handed down by history. And yet
from such scant experience we rashly judge what is
immense and eternal. It is as if we were to examine
a tiny portion of a painting and discern there nothing
but a confused mass of colors without design and with-
out art. In the universe, in short, the part can be
disturbed without prejudice to the whole, which will
inevitably escape whomever, like man, has only a
partial vision of things. The theme is taken up again
by Leibniz on many occasions in the Théodicée (1710)
and in the Principes (1718).

We have seen how the principle of plenitude—by
virtue of which all possible things pass into actual
existence (the criterion of compossibility being the only


limiting factor)—was connected, in Leibniz, with that
of sufficient reason. Of this latter principle Lovejoy
([1936], pp. 145-49, 165-80) gives an interpretation
intended to show its affinity with Spinoza's kind of
determinism. According to Lovejoy, the principle of
sufficient reason, with its criterion of compossibility as
sole restriction in the passage from the possible to the
actual, is not substantially different from the universal
necessity of Spinoza; and absolute logical determinism
would then be characteristic of the thought of both.

This interpretation of the principle of sufficient rea-
son and of the consequent justification of moral and
physical evil helps clarify the special nature of Leib-
nizian “optimism,” and in general of eighteenth-
century optimism of Leibnizian derivation; and also
helps explain how it could coexist with a description
of man's place in the universe which certainly does
not seem, at first, to encourage an optimistic vision
of the human condition. It was not a question of deny-
ing the existence of evil but rather of showing the
necessity for it—and this was done in the face of the
most dismal and grim descriptions of a natural and
moral reality in which this same passage from possi-
bility to reality shaped up as a struggle for existence.
This is a recurrent motif in the theological and moral
writings of the time, and there is an echo of it in Pope's
Essay on Man (1734), a great popularizer of the idea
of the Chain of Being and its implications. The contrast
between such avowed optimism and this taste for the
grimmest descriptions of the human condition did not
escape Voltaire, the most famous critic of the optimism
of his day: Vous criez “Tout est bien” d'une voix lamen-
he observed; and he invited his adversaries to
cease proposing the immutable laws of necessity as
explanation of evil.

In this plan of a perfect universe in which outrageous
(and necessary) afflictions of individuals are embraced
and given a new value in the law of universal harmony,
a not inconsistent feature was the idea that man, far
from being the king of creation and the measure of
all things, was a mere link in the Chain of Being,
infinitely farther from the highest grades of creation
than he is above the lowest of creatures. This too is
a recurrent motif in the literature of the time.

An argument in favor of political conservatism fol-
lowed from all of this: if the perfection of the divine
plan requires a universe ordered in a hierarchy of
beings, each destined to occupy a place in the scale
of creatures so that all gradations are filled, then the
same law should prevail in the world of men, or the
moral universe: the norm of behavior should be to live
in keeping with one's condition, without subverting any
order of society which, like a microcosm, reflects the
very order of the universe.


1. Two Objections. There seems to have been only
two dissident voices in this ideal climate, namely, those
of Dr. Johnson and Voltaire. Samuel Johnson (in 1757)
applied Zeno's argument to the Chain of Being.

The Scale of Existence from Infinity to Nothing cannot
possibly have Being. The highest Being not infinite must
be... at an infinite Distance below Infinity... and in
this Distance, between finite and infinite, there will be
Room for ever for an infinite series of indefinable Existence.
Between the lowest positive existence and Nothing,... is
another chasm infinitely deep; where there is room again
for endless Orders of subordinate Nature.... Nor is this
all. In the Scale... there are infinite Vacuities. At whatever
Distance we suppose the next Order of Being to be above
Man, there is room for an intermediate Order of Beings
between them; and if for one Order, then for infinite Orders;
since every Thing that admits of more or less, and conse-
quently all the Parts of that which admits them, may be
infinitely divided...

(A Review of a Free Inquiry into the
Nature and Origin of Evil

Johnson's argument, as we see, strikes directly at the
foundation of the Chain of Being—the principle of
plenitude. Still, with a moment's reflection, we see that
it is not really pertinent: the Chain of Being is, so to
speak, the cosmological translation of Zeno's paradox,
and its fullness is predicated precisely upon the “fault”
Johnson finds with it, namely, that infinite divisibility
which affords the insertion between one order and
another of “endless orders.”

Voltaire, on the other hand, questions on the basis
of empirical observation whether it can be held that
there is a gradation of created beings (Dictionnaire
[1764], s.v. “Chaîne des êtres créés”). It
is gratifying to the imagination, he says, to contemplate
that imperceptible passage from the inanimate to the
organic, from plants to zoophytes, to animals, to angels,
all in ascending grades of perfection up to God Him-
self. This hierarchy pleases the bons gens, who believe
they recognize in it the Pope, followed by the cardi-
nals, archbishops, and bishops, followed in turn by the
curates, vicars, and simple priests, deacons and sub-
deacons, lastly by friars and capuchins. But there is
an essential difference between the cosmological and
ecclesiastical hierarchies: whereas in the latter the
humblest member can be Pope, in the former not even
the most perfect of creatures can become God. And
with this apparently jesting observation Voltaire
catches an essential feature of the Chain of Being—its
immobility: if the principle of plenitude requires that
every grade be filled by an order of creatures, this
hierarchy must necessarily be static, for we cannot
admit a passing onto higher orders which would leave
holes in the universal fabric. And in any case between


even the most perfect of creatures and God an infinite
hiatus must remain (il y a l'infini entre Dieu et lui).

But Voltaire's objection regards, above all, the prin-
ciple of continuity, which is nowhere evidenced in
nature: let the proof of that be that there are extinct
species in both the animal and vegetable kingdoms.
It is probable that even among men there are extinct
species; and between apes and men there is clearly
a gap. As for spiritual substances, Christians believe
in them because faith teaches that these substances
exist; but what reason had Plato for believing so? And
finally how can there be in empty space a chain that
binds all? Here Voltaire catches another difficulty in
the idea of a continuum, namely, one owing something
to the philosophy of Newton, who had affirmed the
existence of a vacuum—something rejected by Leibniz
in favor of the plenitude hypothesis.

Of the two criticisms presented above, Johnson's in
its logical strictness misses the mark because he chal-
lenges the principle of plenitude precisely on the basis
of the idea that makes it possible, namely the infinite
divisibility of matter. Voltaire's is the more interesting
because it reflects the debates current in the biological
sciences of his day, and especially the discussions of
the notion of species, which, as we shall see, were to
be decisive in the development and eventual dissolu-
tion of the Chain of Being.

2. Kant's Criticism and the Chain of Being. In the
Allgemeine Naturgeschichte und Theorie des Himmels
(1755), Kant takes up the Leibnizian argument of the
coincidence in God of the possible and the actual:
creation is surely commensurate with the power of an
infinite being, and it would be nonsense to say that
God allows only a minimal part of his creative poten-
tial to pass into actuality. It is more reasonable to
suppose that divine creativity does not unfold all at
once but gradually, that creation has indeed a begin-
ning but no end. In the formation of worlds, the first
elements of chaos already bear the signs of that com-
pleteness that is of the very nature of their origin, since
their nature can only be a consequence of the eternal
idea of the divine intelligence. Matter itself has within
it the tendency to organize itself, through natural
evolution, in always more perfect forms.

Here, as we see, Kant gives us what Lovejoy ([1936],
Ch. IX) later called a “temporalized” version of the
Chain of Being, in which creation takes the form of
a natural development starting from the divine idea;
and it comes about step by step, filling up space with
worlds in the process of eternity. It is an evolutional
ebb and flow in which worlds are formed and dissolved;
but the production of ever new worlds guarantees the
fullness and infinite variety of the whole. If in its
temporal variations a system exhausts all the variety
of which it is constitutionally capable, it becomes a
useless member of the Chain of Being, and so performs
its last act in the vicissitudes of cosmic change, paying
its tribute to mortality.

The problem of the Chain of Being is taken up in
very different terms in the Critique of Pure Reason
(1781), and precisely in the Appendix to the Transcen-
dental Dialectic. Here Kant examines the principles
of plenitude and continuity still operative in the sci-
ences of the time, in order to reduce them to “ideas
of the Reason” (transcendental ideas), which as such
have no “constitutive” use but a purely “regulative”
one, that is to say, they are capable of directing the
Understanding to a certain aim, conferring upon its
concepts the greatest unity and extension. Even lying
quite outside the limits of possible experience, the ideas
of the Reason constitute the systematic unity of knowl-
edge. By virtue of this “transcendental presupposition”
we may assume a homogeneity in the apparent infinite
diversity of nature, a unity of its fundamental proper-
ties. This is the scholastic principle of Ockham, “enti-
ties are not to be multiplied more than are necessary”
(entia praeter necessitatem non esse multiplicanda); and
it is the foundation of logical classification. Beside this
principle, which Kant calls the “principle of homo-
geneity,” and which allows the reduction of the various
species to subsumption in a few genera, also at work
in the reason is the “principle of specification,” which
requires a multiplicity and difference among things in
spite of their grouping in a same genus. Each genus
requires diverse species, and each species diverse sub-
species; and

as none even of these subspecies is without a sphere...
reason in all its extension requires that no species should
in itself be considered as the lowest, since the species being
always a concept containing only that which is common
to different things,... it must always subsume other con-
cepts or subspecies. This principle of specification might
be formulated thus: entium varietates non temere esse minu-

(“the variety of things is not to be minimized”).

What Kant calls the law of specification is precisely
the principle of plenitude. Inasmuch as it is an ideal
of the reason it cannot be inferred from experience,
since empirical specification goes no farther than ob-
servable multiplicity; but it is a regulative principle
of experience, since it invites reason to seek the “dis-
tinctive and to presuppose it ever anew, although not
immediately manifest to the senses.” From the two
foregoing principles—homogeneity and plenitude—
there also arises the principle of the continuity of
forms, which provides a continuous transition from
species to species by means of a gradual building up
of differences. Since


... there is no void in the entire sphere of all possible
concepts, and as nothing can be discovered outside this
sphere, there arises the principle non datur vacuum for-
that is to say, there are no different original and
first genera, isolated and separated from each other, as it
were by an intervening void, but all the different genera
are divisions of only one supreme and general genus. From
that principle springs its immediate consequence, datur
continuum formarum,
that is, all the differences of species
border upon one another and admit of no transition from
one to another per saltum.... This logical law of the
continuum of species (continuum specierum) presupposes a
law of continuity in nature (lex continui in natura), which
however remains only thinkable, not knowable: This conti-
nuity of forms is a mere idea, for which it is not possible
to find a corresponding object in experience, not only be-
cause the species in nature are actually divided, and must
form, each by itself, a discrete quantity (quantum dis-
),... but also because we can make no determinate
empirical use of this law, since it does not offer the least
criterion to tell us how and how far we ought to seek for
different grades of affinity; the law of continuity tells us
only in general that we ought to seek for them....

In short, there is no empirical use of the principle of
continuity; it has only a regulative use: as simply an
idea, it serves only to alert us in general that a series
should be sought in nature.

The same can be said, Kant goes on, of the “famous
law” of the Scale of Creatures, consequence of the two
principles in question. The notion of a Chain of Being
is not objectively verifiable by observing nature: “the
steps of this scale, so far as we are able to know them
by experience, are much too far apart, and the (puta-
tively) small differences in nature itself are ordinarily
crevices so vast, that such observations cannot be relied
upon.... ” Even the idea of a Chain of Being, then,
is a regulative principle only, a “method” according
to which we seek order in nature—but a method that
“goes too far for experience or observation to match.”

Thus the Chain of Being is reduced, in Kant, to one
of those ideals for which there is no empirical appli-
cation, and which indeed, in their empirical use, can
produce only imaginary knowledge and hence eternal
contrasts and contradictions. And with that an essential
aspect of the Chain of Being is wanting: its function,
namely, as a scheme of nature that observation is
supposed to fill in gradually by reconstructing it em-
pirically. Such a reconstruction, for Kant, is not possi-
ble: it would indeed constitute an example of the
dialectic of appearance. In these same decades, and
no doubt independently of the Kantian criticism, the
biological sciences produced a profound transformation
in the idea of a Chain of Being; and at the end of
this process the conclusion emerges that it is impossible
to reconstruct in a scientific way the hierarchical
structure of the universe. In this way that fixed struc-
ture loses all objective validity and is no longer one
of the constitutive principles of scientific research.


1. Crises of the Chain of Being: The Controversies
over the Notion of Species.
We have said that for Kant
the empirical use of ideas such as that of continuity
and of the plenitude of forms (plenum formarum) was
illegitimate and could only make for contradictions and
controversies. His conclusion seems to be, and indeed
is, in part, a commentary on the eighteenth-century
discussions of continuity and plenitude in the biological

At first the new instruments of scientific research do
not seem to contradict the idea of a Scale of Creatures.
Indeed, the already widespread use of the microscope
makes it possible to observe the world of the infinitely
small; and in 1739 the discovery of Trembley's Hydra
is hailed as the discovery of the missing link between
the vegetable and animal worlds. Even the skeptical
“Pyrrhonism” of men of science, or their awareness
of the limitations of experimental research, echoes
Leibniz' vision of a universal “plenum” of which we
have a partial vision only. No, it is rather the debate
over the notion of biological species that challenges
the foundations of the Chain of Being, and in particular
the principle of plenitude. In order to salvage this
principle it was necessary to attribute only a conven-
tional, not real, value to biological classifications: sub-
division into species would in fact have created in
nature a too nicely spaced series, letting precisely those
imperceptible gradations escape which assure conti-
nuity and plenitude in the natural world.

The conventionality of species is affirmed in Buffon's
Discours sur la manière d'étudier et de traiter l'Histoire
which prefaces the first volume of his Histoire
(1748). The methods or “systems” of classifi-
cation are, to be sure, indispensable but artificial: as
against the nuances of natural reality we have an arbi-
trarily articulated series. The error of all classification
rests on the inability to grasp the processes of nature,
which are always realized by degrees, by imperceptible
nuances, thus escaping all division. In short, only indi-
viduals exist in reality; genera or species do not.

But Buffon wholly reversed his position in the course
of his research, prompted by the now general recogni-
tion of species as a genetic entity. In fact, in Volume
XIII of the same work (1765) he affirms that the only
true beings in nature are species and not individuals.

Robinet, a firm advocate of the principle of pleni-
tude, was quite clear about the dangers inherent in
classifications: if we accept the separation of nature
into orders of this kind, the Chain of Being is fatally


broken (De la nature [1766], IV, 4-5). Doubtless the
introduction of the idea of species as a genetic entity
contributed decisively to this crisis of the principle of
plenitude: since two individuals are said to belong to
the same species if they are capable of producing a
fertile offspring and of transmitting to it their own
hereditary characteristics, it is hard to imagine a “full”
concatenation among the diverse species. Actually, in
the second half of the eighteenth century, the notion
of species is already established and operative in the
biological sciences. The controversies—accelerated by
the always growing body of empirical data, and par-
ticularly by the data of the new science of paleon-
tology—had to do rather with the fixity or nonfixity
of the species (taken now as established entities).

2. Crisis of the Chain of Being: Permanence and
Becoming in Nature.
In a world hierarchically ar-
ranged, such as the one described by the great meta-
phor of a Chain or scale of beings, orders of creatures
had to be considered fixed ab aeterno with their essen-
tial and thus unalterable characteristics. In the third
decade of the century Réaumur wrote: “The author
of nature wanted our earth to be populated with a
prodigious number of species of animals, and has given
the earth those species fit for it to possess....” And
again: “One must start from the principle that the
species of insects are—no less than those of animals—
invariable in form” (Mémoires pour servir à l'histoire
des insectes
[1734-42], II, XL-XLI). The physician
Antonio Vallisnieri (1661-1730) affirmed on anatomical
grounds that it was impossible for carnivorous habits
to be acquired: it is no accident (only to regret it
afterward) that God, immutable and omnipotent,
wanted herbivores to be so different from carnivores:
such difference is but another proof of the unalterable
structure of that great theater that is nature (Opere
I, 315A). In general all adaptation phe-
nomena should be interpreted not as chance environ-
mental mutations but as providentially preordained
laws (ibid., I, 137B). The fixity of species is also basic
to Linnaeus' Philosophia botanica (1751).

Faith in the permanence of nature (required by the
idea of the Chain of Being) and the affirmation that
there is evolution in nature are clearly contradictory:
mediating between them was a theory of the preexis-
tence of seeds—already diffuse, beginning from the last
decades of the seventeenth century—according to
which every living thing would exist already formed
in all its parts in the seed, and all seeds, created ab
would simply be transmitted and developed in
reproduction. With such a doctrine—adopted by Fon-
tenelle and Leibniz among others—one could conceive
of the history of nature as explication and development
of all those possibilities already foreseen ab aeterno as
essential parts of the world's structure.

This transformist view afforded a reconciliation of
the idea of plenitude with that of the perfectibility
of nature. And in this sense it is used, for example,
by Robinet in his De la nature (1761-68). In a word,
natural development, if seen as development of matu-
ration of preexisting seeds, adds nothing really new to
creation but simply explicates its original productivity.
Nature is continuously working itself out, and the
principle of plenitude is manifest in this temporal

Yet just this transformism was bound to challenge,
explicitly or implicitly, the notion of the fixity of spe-
cies and thus precipitate a crisis in the hierarchical
image of the cosmos. But for that matter numerous
and grave objections to the fixity of species were being
raised by the necessity to give some plausible account
of hereditary and adaptation phenomena, which re-
quire the intervention of variation and of environ-
mental determination. Remarkable how Maupertuis in
his Essai de cosmologie (1750), precisely by reflecting
upon adaptation phenomena and the natural selection
that implies, was led to draw the same conclusion that
Kant was to draw some years later, in regard to the
illegitimacy of the empirical use of the principles of
plenitude, of homogeneity, and of continuity. Only
those species that have certain adaptable relations
(rapports de convenance) with nature may survive.

One would say that chance has produced an incalculable
multitude of individuals; a small number happened to be
so constructed that the parts of each creature were capable
of satisfying its needs; in another number, infinitely larger,
there was neither adaptability nor order; such species have
all perished... and the species that we see today are the
tiniest part of all a blind destiny has produced

(Essai, in
Oeuvres [1756], I, 11-12).

The continuity of the natural world can never be, then,
an empirical statement: uniformity is (as we may say)
a spiritual exigency and has no exact counterpart in
experience: Continuity pleases our mind, but does it
please Nature? (Elle plaît à notre esprit, mais plaît-elle
à la Nature?
—ibid., 51). The Chain of Being, thanks
to which we may imagine a universe so constituted
that the beings that fill it can only be the perfectly
juxtaposed parts of the whole, was perhaps broken up
by some telluric cataclysm; however that may be, it
cannot now be reconstructed on the basis of observa-
tion. And it is for this reason that Maupertuis, in the
third part of his Essai, presents it as pure conjecture.

But even more telling than Maupertuis' Essai of the
new philosophy of nature is his Système de la nature
(first ed., in Latin, 1751), wherein we witness the disso-
lution of that bond between natural forms and divine
creativity which had, from the Timaeus on, formed the
basis of the Chain of Being. To suppose that all indi-


viduals were made by the divine will on one and the
same day of creation, says Maupertuis, means to have
recourse to a miraculous rather than physical explana-
tion. The laws at work in nature, which are the only
object of science, operate to conserve and also to
transform natural forms (French edition [1756], sec-
tions XI-XLIX).

The importance of this new conception of the rela-
tions between God and nature is certainly the decisive
element in the dissolution of the Chain of Being. As
Roger has observed ([1963], pp. 486-87), Maupertuis,
rejecting the preexistence of seeds, the notion of God
as “maker,” and the fixity of forms, was led to study
the life of natural forms in time, introducing duration
into biological sciences as an essential element. This
general temporalization of nature is a particular exam-
ple of what Lovejoy has called ([1936], p. 242) the
“temporalizing” of the Chain of Being. According to
the traditional conception, the Scale of Creatures was
static and the temporal process brought no enrichment.
In the new “temporalized” version the plenum for-
was conceived instead “not as the inventory
but as the program of nature, which is being carried
out gradually and exceedingly slowly in cosmic history”
(ibid., p. 244).


1. The Principle of Continuity in the Philosophy
of Becoming.
We have seen from the beginning how
the idea of the Chain of Being was founded on two
basic principles: the principle of plenitude and that
of continuity. In the history of the idea, as we have
been reconstructing it, these two principles not only
go together but at times indeed coincide. But we should
not forget that they have completely different and
independent origins. The principle of plenitude—of
Platonic origin—was born of an essential attribute of
the Demiurge or Creator God, and that is His super-
abundance and necessary creativity; it is therefore
bound up with the principle of sufficient reason, as
Leibniz tells us quite explicitly. The principle of conti-
nuity, on the other hand, is a biological one, arising
from the observation that there exist beings hardly
reducible to one or another of the great classes into
which all natural things seem to fall. Now the different
origin of these two principles should be borne in mind
in retracing the dissolution of the Chain of Being.

The question of the existence or nonexistence of
species in nature ended up in a crisis for the principle
of plenitude: if one acknowledged the real, objective
existence of those genetic entities called species, it was
hard to picture nature except as a series of distinct
units—which of course contradicted the principle of
plenitude. It was not however impossible to imagine
a continuity in the series—a continuity subsisting
somehow between the inorganic and the organic, be-
tween the vegetable and animal worlds: witness, for
example, the position of Buffon. We have seen that
he had come in the course of his research to reverse
his first denial of the existence of species, indeed to
the point of affirming that they are the only natural
reality; and yet he never denied the unity and continu-
ity of nature. And this in the name of the experimental
method, which should always remind us of the abstract
character of definitions, and distinguished the name
from the thing. Once a definition is accepted, writes
Buffon in Chapter VIII of his Histoire des animaux
(1749), it is imagined that the word is a line of demar-
cation among the products of nature; that, for example,
all above a certain line “should be really animal, and
that everything below be nothing but vegetable....
But as we have already said many times, these lines
of demarcation do not exist in nature.” The same con-
tinuity—unity between inorganic and organic, between
animal and man, unity in the perpetual flux of
things—is amply witnessed in the writings of Diderot
in the Rêve de d'Alembert: “All creatures merge into
one another... all in perpetual flux.... Every animal
is more or less a man; every mineral is more or less
a plant; every plant is more or less an animal. There is
nothing precise in nature.” (Tous les êtres circulent les
uns dans les autres... tout est dans un flux perpétuel.
... Tout animal est plus ou moins homme; tout minéral
est plus ou moins plante; toute plante est plus ou moins
animal. Il n'y a rien de précis dans la nature.
) Even
Robinet, in the name of the principle of continuity,
denies that the organic and the inorganic are quite
different, to the point of attributing a kind of rudimen-
tary reason to matter even in its inorganic phase. Ac-
cording to La Mettrie nature seems to proceed, so to
speak, by trial and error towards greater and greater
organization, and it is just this that assures its unity:
there is a kind of “imperceptibly graduated scale” in
the sensory faculties, from plant to animal to man; and
nature “passes through all gradations without skipping
a single one in all its various productions” ( L'homme-
[1748], in Oeuvres [1796], II, 69). J. T. Needham
too, rejecting the fixity of natural forms, considers the
gradation in nature as the result of a progressive orga-
nization (cf. the Philosophical Transactions of the Royal
45 [1748], no. 490). Robinet and Bonnet debate
at length the problem of reconciling the idea of a Chain
of Being with that of the evolution of forms. In general,
then, a latent vitalism, introducing the idea of a teleol-
ogy inherent in matter, tends more to fill than to
accentuate the breaks among the different orders of
natural reality.

In the second half of the eighteenth century, then,
the temporalization of the natural sciences disparages
but does not eliminate the idea of a biological con-


tinuum which, as we have seen, persists as a recurrent
topos in the scientific thought of the time. It persists
however, in a very different formulation from the
traditional one: not as gradation and contiguity of
natural forms, but as (temporal) continuity in the orga-
nizational process of nature. And as such it goes well
beyond the eighteenth century, surviving in the bio-
logical vitalism of the following century, up to Berg-
son's élan vital. In general we might say that in all
philosophies of becoming—vitalism, post-Kantian ide-
alism, evolutionism—continuity is adopted as (to use
Kant's term once more) a “regulative ideal,” capable
only of assuring the unity of becoming. Even the doc-
trine of evolution can be understood as a temporal
translation of the continuity principle. It is no accident
that one of the most recent theorists of evolution avails
himself of it, not only as criterion for the interpretation
of nature but as the foundation of a “new humanism.”
Writes Julian Huxley: “... all aspects of reality are
subject to evolution, from atoms and stars to fish and
flowers, from fish and flowers to human society and
values—indeed... all reality is a single process of
evolution.... ” The biological process “takes place in
a series of steps or grades, each grade occupied by a
successive group of animals and plants, each group
sprung from a preexisting one and characterized by
a new and improved pattern of organization.” This
assures the kinship of man with nature: “he now knows
that he is not an isolated phenomenon, cut off from
the rest of nature by his uniqueness. Not only is he
made of the same matter and operated by the same
energy as all the rest of the cosmos, but... he is linked
by genetic continuity with all the other living inhabit-
ants of his planet” (“The Evolutionary Vision,” in
Evolution after Darwin, 3 vols., Chicago [1960], III,

But this survival of the principle of continuity is by
itself not enough to guarantee the survival of the Chain
of Being, even in its temporalized form. Of inde-
pendent origin, the idea of continuity contributes to
the development of the idea of the Chain of Being
only insofar as continuity is associated with, or indeed
fused with, the principle of plenitude. And, surviving
the principle of plenitude (though in a profoundly
changed way), the idea of continuity also survives the
idea of a Chain of Being, which was grounded essen-
tially in the principle of plenitude.

2. From the Chain of Being to the Tree of Life.
As should be clear from the foregoing, the frequent
references to the concatenation of creatures in
eighteenth-century science (with, perhaps, an excep-
tion for Robinet) appeal rather to the principle of
continuity than to that of plenitude. Now although
continuity is an idea implicit in that of plenitude, the
converse is not true. That nature makes no jumps—and
no scientist in the second half of the eighteenth century
appeared to doubt it—does not in fact mean that
nature realizes all those possibilities implicit from all
eternity in the act of creation. The world's continuity,
in other words, is due to the action of laws and forces
and not to a necessity inherent in the divine nature.
And with that the very foundation of the principle of
plenitude, namely, its connection with the principle of
sufficient reason stressed by Leibniz, is broken down.

Typical in this sense is, once again, Buffon's position,
when he places the principle of sufficient reason
among moral entities (êtres moraux), created by man
on the basis of arbitrary relations which can produce
rien... de physique et de réel,” and can never be-
come a “physical reason” for things. It is therefore
illegitimate to ask ourselves the “why” of nature (His-
toire des animaux,
Ch. V). Science no sooner rejects
the principle of sufficient reason than it does the prin-
ciple of plenitude, that is, the very foundation of the
Chain of Being. The principle of continuity which, as
we have seen, survives the process of temporalization,
is by itself not enough to guarantee the survival of the
Chain of Being. And the best epitaph, at the conclusion
of this sketch, might be one from the same Buffon:
le vivant et l'animé, au lieu d'être un degré méta-
physique des êtres, est une propriété physique de la
(“Animated life, instead of being a metaphysi-
cal grade of being, is only a physical property of mat-
ter,” ibid., Ch. I).

The succession of living forms appears explainable
now on the basis of the working of physical laws or
of an activity inherent in nature: nature, as La Mettrie
says, is “neither Chance, nor God” (ni Hasard, ni Dieu).
The certainty of this descending process, from God to
the natural world, fails; and with that is lost too the
presumption that science can reconstruct the plan of
creation in all its fullness by working its way back per

Now we may say that the divorce between the two
ideas, that of continuity and that of plenitude, is com-
plete, even though they appear associated once more
in romantic philosophy: in Schiller's dialectic of
Formtrieb and Stofftrieb; in Fichte's conception of the
Ego as infinite activity; in the philosophy of nature
of Schelling; in the ethico-political ideal of the reach-
ing of moral perfection through an indefinite progress;
and in the conception of aesthetic progress as infinite

In science, the metaphor of the Chain of Being was
to continue to circulate long after its “crisis”; the
English paleontologist James Parkinson, still in the
second decade of the nineteenth century, saw in it an
obstacle to the correct interpretation of the data of


the new science (Greene [1959], p. 122). But in general,
in nineteenth-century science, another metaphor gains
currency, one that keeps the quality of continuity but
not of plentitude. It is the tree of evolution, published
by Lamarck in the Philosophie zoologique ([1809]; re-
produced in Greene, p. 163), which represents a series
branching off in an irregularly spaced but uninter-
rupted way. It is what Darwin calls the “Tree of Life”
(Origin of Species [1859], Ch. IV).

The affinities of all beings... have sometimes been repre-
sented by a great tree. I think this simile largely speaks
the truth. The green and budding twigs may represent
existing species; and those produced during former years
may represent the long succession of extinct species. At each
period of growth all the growing twigs tried to branch out
on all sides, and to overtop and kill the surrounding twigs
and branches, in the same manner as species and groups
have at all times mastered other species in the great battle
for life.... As buds give rise by growth to fresh buds, and
these, if vigorous, branch out and overtop on all sides many
a feebler branch, so by generation I believe it has been
with the great Tree of Life, which fills with its dead and
broken branches the crust of the earth, and covers the
surface with its ever-branching and beautiful ramifications.


The historian of the idea of the Chain of Being is Arthur
O. Lovejoy. The present article is predicated upon his
exemplary study, The Great Chain of Being. A Study of the
History of an Idea
(Cambridge, Mass., 1936; 1961).

We cannot here provide a bibliography for all the authors
touched on and for all the different themes involved in one
way or another with the idea of the Chain of Being. How-
ever, the following are certain studies to which (although
they may not deal specifically with the subject in question)
the present article is indebted for clarification and useful

For the influence of the Timaeus and the continuity of
Platonic thought to the Renaissance: H. Lyttkens, The
Analogy between God and the World
(Uppsala, 1953; 1955);
T. Gregory, Anima mundi (Florence, 1955); E. Garin Studi
sul platonismo medievale
(Florence, 1958); R. Klibansky
“The School of Chartres,” Twelfth-Century Europe and the
Foundation of Modern Society
(Madison, 1961).

For the connection between the Scale of Nature and the
classification of the sciences from the Middle Ages to the
Renaissance: T. Carreras y Artau and J. Carreras y Artau,
Historia de la filosofía española (Madrid, 1939), I, 233-640;
J. Carreras y Artau, De Ramón Lull a los modernos ensayos
de formación de una lengua universal
(Barcelona, 1946); P.
Rossi, Clavis universalis (Milan and Naples, 1960).

Fundamental for knowing the background of the devel-
opments of the Chain of Being in scientific thought from
the late Renaissance to the late eighteenth century are: J.
Roger, Les sciences de la vie dans la pensée française du
XVIIIe siècle
(Paris, 1963), esp. Part III (“La science des
philosophes,” pp. 457-761); The Forerunners of Darwin, ed.
B. Glass (Baltimore, 1959; 1968), containing among other
things an essay of Lovejoy on Buffon (“Buffon and the
Problem of Species,” pp. 84-113). There is something on
the Chain of Being in S. Toulmin and J. Goodfield, The
Discovery of Time
(London, 1965). See also: Roots of Scien-
tific Thought,
ed. Philip P. Wiener and Aaron Noland (New
York, 1957), Pt. 4; C. Greene, The Death of Adam: Evolution
and its Impact on Western Thought
(Ames, Iowa, 1959); and
Leibniz Selections, Philip P. Wiener, 2nd ed. revised (New
York, 1966).


[See also Conservatism; Continuity; Creativity; Evil; Evo-
lutionism; God; Hierarchy; Macrocosm; Neo-Platonism;
Perfectibility; Romanticism in Post-Kantian Philosophy;