I. PRE-NEWTONIAN PHILOSOPHERS
IN ENGLAND
The methodological discussions of Francis Bacon,
Thomas Hobbes, and Robert
Boyle are of special inter-
est because they
exhibit a variety of reactions among
advocates of the new science to the
traditional distinc-
tion of four kinds of
causation. Professedly and more
or less heatedly antischolastic, they
shared the corpus-
cular view that the
phenomena of nature were to be
explained by the motion of small particles
or corpus-
cles. Yet each of them made use of
scholastic terms
in distinguishing kinds of causal explanations.
In the classification of sciences in Book III, Ch. IV,
of De augmentis scientiarum (1623), Bacon distin-
guished four kinds of causes. The
investigation of na-
ture was divided in two
parts: physics was to be con-
cerned with
efficient and material causes, while
metaphysics was to deal with final and
formal causes.
Explaining this classification, Bacon cautioned his
reader that, although he was continuing to use tradi-
tional terms, he felt free to alter their senses; and
it
is clear that his view differed from that of his scholastic
contemporaries in at least three important respects.
First, metaphysics,
which was distinguished from first
philosophy and natural theology, was a
part of natural
philosophy; and to metaphysics he assigned what he
took to be the most important and productive part of
his new
science—the investigation of forms or formal
causes. Second,
although the investigation of final
causes was also within the province of
metaphysics,
it, unlike the investigation of forms, could provide no
knowledge of physical causes. Although it made sense
to assert
“that the firmness of hides in animals is for
the armour of the
body against extremities of heat or
cold,” such an explanation
did not specify the actual
physical cause of the phenomenon; and it was,
accord-
ing to Bacon's frequently cited
condemnation, “barren
and like a virgin consecrated to God
produces nothing”
(Book III, Ch. V). Third, the term forma underwent
a sea change in Bacon's philosophy.
Aware of Platonic
and Aristotelian connotations, he explained in Novum
organum (1620) that, when he used this term
to refer
to what was to be discovered in the productive part
of
metaphysics, he did not mean “abstract forms and
ideas, either
not determined in matter at all, or ill
determined” (Book II,
Aphorism xvii). His forms could
be discovered, and could be precisely
determined, by
“true induction,” i.e., by the method
of “rejection or
exclusion.” An investigation of the
form of heat, for
example, showed that it was a species of motion: spe-
cifically, a motion that was
“expansive, restrained, and
acting in its strife upon the smaller particles of
bodies”
(Book II, Aph. xx).
Although motion of this kind was said to be the cause
of heat, Bacon
carefully distinguished this cause from
what he called the
“efficient cause” of heat. The term
“efficient cause” was reserved for the results of investi-
gations of a quite different and
less fundamental nature
that were to be a part of physics, namely,
investigations
of the ways in which bodies could be heated. Holding
that heat could be produced in a body in various ways,
he maintained that
the efficient cause was variable or,
in J. S. Mill's terms, that there was
a plurality of
efficient causes of heat. By contrast, what was discov-
ered by “rejection or
exclusion” was universally present
in all hot bodies; and Bacon
seems to have called this
species of motion the
“form” or “formal cause” of
heat
because he thought that, in making this discovery, he
had
discovered what heat really was—its nature or
essence—and not something that was distinct from heat
and, in
Hume's terms, was “constantly conjoined” with
it. In
a passage in which he was concerned to explain
precisely what he meant, and
what he did not mean,
when he asserted that heat was a species of
motion,
he expressed this thought quite clearly. He did not
mean, he
explained, that “motion generates heat”;
rather, his
conclusion was that “Heat itself, its quid
ipsum, is Motion and nothing else...” (Book II,
Aph.
xx). Although Bacon was not always as clear as he was
in this
passage about the nature of conclusions reached
by “rejection or
exclusion,” the view that he was at-
tempting to formulate in this passage was, in more
recent
terminology, that the most basic laws of science
were contingent statements
of identity; and he care-
fully distinguished
these laws from conclusions of lesser
consequence about efficient causes
and also material
causes.
Examining the metaphysicians' view of causation in
De corpore (1655), Hobbes claimed that the only
tenable
distinction within the fourfold classification was that
of
efficient cause and material cause (Part II, Chs. IX
and X). What the
metaphysicians classified as final
causes and formal causes—ends
and essences, respec-
tively—were, according to Hobbes, really efficient
causes. Ends, he maintained, could be ascribed only
to what had sense and
will; and the end of a desire
was the object desired. On his view, however,
the
object desired was the efficient cause of the motion
that
constituted the desire; and, whereas it seemed “as
if we draw
the object to us,” what was really the case
was that
“the object draws us to it by local motion”
(“Short Tract on First Principles,” Appendix I in The
Elements of Law, ed. F. Tönnies,
Cambridge, 1928).
Taking the scholastics' view about formal causes to
be
that “the essence of a thing is the cause thereof, as
to be rational is the cause of man...,” there is
little
wonder that Hobbes deemed the view unintelligible.
Yet he was
not prepared to deny that essences func-
tioned as causes: “knowledge of the essence of any-
thing,” he
maintained, “is the cause of the knowledge
of the thing itself;
for, if I first know that a thing
is rational, I
know from thence, that the same is
man...” (De
corpore, Part II, Ch. X). Essences were
causae cognoscendi, but Hobbes insisted that, as
such,
they were efficient causes, or rather parts of the ef-
ficient causes, of the knowledge that
resulted from
knowledge of them.
Hobbes retained the terms “efficient cause” and
“material cause” to mark a distinction within what he
called the “entire cause” or “cause
simply.” Antici-
pating Mill's
view about a philosophical sense of
“cause,” the
entire cause was for him “the aggregate
of all the accidents
both of the agents how many soever
they be, and of the patient put
together; which when
they are all supposed to be present, it cannot be
under-
stood but that the effect is
produced...; and if any
one of them be wanting, it cannot be understood
but
that the effect is not produced” (Part II, Ch. IX).
Since,
on his view of bodies, there was no substantial change,
every
change was a change of an attribute or accident
of a body; and the cause,
or “entire cause,” included
all of the many
attributes of the agent and patient
bodies that were necessary and jointly
sufficient for the
occurrence of the change. Realizing that not just
one
condition but many were necessary and that the term
“cause” was usually used to refer to only one of
these
conditions, he distinguished the “entire cause”
and the
cause sine qua non and tried to state
the criterion used
in the selection of one of the many conditions as
the
“cause,” in the ordinary sense of the term, or cause
sine qua non. In this attempt, he seems not to
have
been successful, but he did make clear what he (if not
others)
meant by “material cause” and “efficient
cause.” The totality of conditions necessary for the
occurrence
of a change included attributes of the body
acted upon, for instance,
dryness of wood that was
ignited, as well as attributes of the agent body
or
bodies. The former were the material cause, and the
latter the
efficient cause.
When Hume claimed that all causes were of the
same kind, he seems to have
been aware of one of the
distinctions that Hobbes made. In the passage
quoted,
he claimed to find no basis for a distinction
“betwixt
efficient causes, and causes sine
qua non....” Holding
himself that “the
same cause always produces the same
effect, and the same effect never
arises but from the
same cause” (A
Treatise..., Book I, Part III, Ch. XV),
he seems not to have been
aware of the problem that
Hobbes discovered in the discrepancy between a
defi-
nition of “cause” in terms of necessary and
sufficient
conditions and the ordinary use (Hume's included) of
this
term.
Boyle was more hospitably disposed toward expla-
nations in terms of final causes than Hobbes or Bacon.
Concluding his discussion of final causes in The Use-
fulness of Experimental Natural
Philosophy (1688), he
maintained that “as to animals,
and the more perfect
sorts of vegetables, it is warrantable, not
presumptuous,
to say, that such and such parts were preordained to
such and such uses, relating to the welfare of the animal
(or plant)
itself, or to the species it belongs to....”
Yet he exhorted the
true “naturalist” not to “let the
search
or knowledge of final causes make him neglect
the industrious indagation
[i.e., investigation] of effi-
cients,” and he implied that the naturalist's principal
aim was the discovery of efficient causes. This supposi-
tion in Boyle's discussion of methodology does not
seem
to accord with the Baconian way in which he stated
the
conclusions of his investigations of the “origin” of
certain qualities. His investigation of heat, for instance,
revealed its
“nature”; and this way of stating his con-
clusion suggests that, like Bacon, he
thought that he
was discovering what heat really was—its nature
or
essence. The apparent inconsistency can be explained
if we
attribute to Boyle a view like John Locke's in
An Essay Concerning Human Understanding (1690),
in
which the term “heat” was used equivocally to refer
both to heat as it existed in bodies and to heat as it
existed in us. (Cf.
Book II, Sec. viii, of the Essay.) Using
“heat” in the first sense, Boyle could represent the
conclusion of his investigation as the discovery of the
nature of heat.
Since what was discovered was also
thought to be the efficient cause of
heat in the second
sense, he could also represent the conclusion of
his
investigation as the discovery of the efficient cause of
heat.
That Boyle used terms like “heat” in two senses
is
evident from his seemingly contradictory statements
about color: color was
not “an inherent quality of the
object,” yet
whiteness—for Boyle, a color—could be
“considered as a quality in the object” and, as such,
“depended on the asperity of the superficies of the
body” (Robert Boyle on Natural Philosophy, ed.
M. B.
Hall, pp. 255-56). Like Locke and unlike Bacon, Boyle
did not
think it important to distinguish two kinds of
investigations of the
phenomenon of heat; and the
conclusion of any investigation was
alternatively about
the nature of heat as it existed in bodies or about
the
efficient cause of heat, i.e., about a power in bodies
to produce
heat in us, and also in other bodies. For
this reason, and because he did
not think that the
nature or cause of heat was directly observable,
there
was no temptation to characterize the aim of causal
inquiry in
Humean terms as the discovery of constant
conjunctions between kinds of objects or events. In the
case of
“forms and qualities,” it was the discovery of
their
“origin.”
