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Dictionary of the History of Ideas

Studies of Selected Pivotal Ideas

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Experimental science owes its beginnings in Western
Europe to the influx of treatises from the Near East,
by way of translations from Greek and Arabic, which
gradually acquainted the Schoolmen with the entire
Aristotelian corpus and with the computational tech-
niques of antiquity. The new knowledge merged with
an Augustinian tradition prevalent in the universities,
notably at Oxford and at Paris, deriving from the
Church Fathers; this tradition owed much to Platonism
and Neo-Platonism, and already was favorably disposed
toward a mathematical view of reality. The empirical
orientation and systematization of Aristotle were wel-
comed for their value in organizing the natural history
and observational data that had survived the Dark Ages
through the efforts of encyclopedists, while the new
methods of calculation found a ready reception among
those with mathematical interests. The result was the
appearance of works, first at Oxford and then at Paris,
which heralded the beginnings of modern science in
the Middle Ages.

1. Origins at Oxford. Aristotle's science and his
methodology could not be appreciated until his Physics
and Posterior Analytics had been read and understood
in the universities. Among the earliest Latin commen-
tators to make the works of Aristotle thus available
was Robert Grosseteste, who composed the first full-
length exposition of the Posterior Analytics shortly after
1200. This work, plus a briefer commentary on the
Physics and the series of opuscula on such topics as
light and the rainbow, served as the stimulus for other
scientific writings at Oxford. Taken collectively, their
authors formed a school whose philosophical orienta-
tion has been characterized as the “metaphysics of
light,” but which did not preclude their doing pioneer
work in experimental methodology.

The basis for the theory of science that developed
in the Oxford school under Grosseteste's inspiration was
Aristotle's distinction between knowledge of the fact
(quia) and knowledge of the reason for the fact (propter
). In attempting to make the passage from the one
to the other type of knowledge, these writers, implic-
itly at least, touched on three methodological tech-
niques that have come to typify modern science,
namely inductive, experimental, and mathematical.

Grosseteste, for example, treated induction as a dis-
covery of causes from the study of effects, which are
presented to the senses as particular physical facts. The
inductive process became, for him, one of resolving
the composite objects of sense perception into their
principles, or elements, or causes—essentially an ab-
stractive process. A scientific explanation would result
from this when one could recompose the abstracted
factors to show their causal connection with the ob-
served facts. The complete process was referred to as
“resolution and composition,” a methodological expres-
sion that was to be employed in schools such as Padua
until the time of Galileo.

Grosseteste further was aware that one might not
be able to follow such an orderly procedure and then
would have to resort to intuition or conjecture to
provide a scientific explanation. This gave rise to the
problem of how to discern a true from a false theory.
It was in this context that the Oxford school worked
out primitive experiments, particularly in optics, de-
signed to falsify theories. They also employed observa-
tional procedures for verification and falsification when
treating of comets and heavenly phenomena that could
not be subjected to human control.

The mathematical component of this school's meth-
odology was inspired by its metaphysics of light. Con-
vinced that light (lux) was the first form that came to
primary matter at creation, and that the entire struc-
ture of the universe resulted from the propagation of
luminous species according to geometrical laws, they
sought propter quid explanations for physical phe-
nomena in mathematics, and mainly in classical geom-
etry. Thus they focused interest on mathematics as well
as on experimentation, although they themselves con-
tributed little to the development of new methods of

2. Science on the Continent. The mathematicist
orientation of the Oxford school foreshadowed in some
ways the Neo-Pythagoreanism and rationalism of the
seventeenth century. This aspect of their thought was
generally rejected, however, by their contemporaries


at the University of Paris, especially Albertus Magnus
and Thomas Aquinas. Both of the latter likewise com-
posed lengthy commentaries on the Posterior Analytics
and on the physical works of Aristotle, primarily to
put the Stagirite's thought at the service of Christian
theology, but also to aid their students in uncovering
nature's secrets. Not convinced of an underlying math-
ematical structure of reality, they placed more stress
on the empirical component of their scientific method-
ology than on the mathematical.

Albertus Magnus is particularly noteworthy for his
skill at observation and systematic classification. He
was an assiduous student of nature, intent on ascertain-
ing the facts, and not infrequently certifying observa-
tions with his Fui et vidi experiri (“I was there and
saw it for myself”). He recognized the difficulty of
accurate observation and experimentation, and urged
repetition under a variety of conditions to ensure ac-
curacy. He was painfully aware of and remonstrated
against the common failing of the Schoolmen, i.e., their
uncritical reliance on authority, including that of Aris-
totle. Among his own contributions were experiments
on the thermal effects of sunlight, which A. C. Crombie
has noted employed the method of agreement and
difference later to be formulated by J. S. Mill; the
classification of some hundred minerals, with notes on
the properties of each; a detailed comparative study
of plants, with digressions that show a remarkable sense
of morphology and ecology; and studies in embryology
and reproduction, which show that he experimented
with insects and the lower animals (Crombie, 1953).
Albert also had theoretical and mathematical interests,
stimulating later thinkers such as William of Ockham
and Walter Burley with his analysis of motion, and
doing much to advance the Ptolemaic conception of
the structure of the universe over the more orthodox
Aristotelian views of his contemporaries.

The best experimental contribution of this period,
however, was that of Peter Peregrinus of Maricourt,
whose Epistola de magnete (1269) reveals a sound
empirical knowledge of magnetic phenomena. Peter
explained how to differentiate the magnet's north pole
from its south, stated the rule for the attraction and
repulsion of poles, knew the fundamentals of magnetic
induction, and discussed the possibility of breaking
magnets into smaller pieces that would become mag-
nets in turn. He understood the workings of the mag-
netic compass, viewing magnetism as a cosmic force
somewhat as Kepler was later to do. His work seems
to be the basis for Roger Bacon's extolling the experi-
mental method, and it was praised by William Gilbert
(1540-1603) as “a pretty erudite book considering the

3. Use of Calculation. Mathematical analysis was
not entirely lacking from scientific investigation in the
thirteenth century. One unexpected source came at the
end of the century in the work of Arnald of Villanova,
who combined alchemical pursuits with those of phar-
macy and medicine. Arnald was interested in quanti-
fying the qualitative effects of compound medicines,
and refined and clarified a proposal of the Arabian
philosopher Alkindi (ninth century) that linked a geo-
metric increase in the number of parts of a quality
to an arithmetic increase in its sensed effect. The ex-
ponential function this implies has been seen by some
as a precursor of the function later used by Thomas
Bradwardine (d. 1349) in his dynamic analysis of local
motion (McVaugh, 1967).

A more noteworthy mathematical contribution was
found, however, in earlier work on mechanics, partic-
ularly in statics and kinematics, that definitely came
to fruition in the fourteenth century. Jordanus Nemo-
rarius and his school took up and developed (though
not from original sources) the mechanical teachings of
antiquity, exemplified by Aristotle's justification of the
lever principle, by Archimedes' axiomatic treatment
of the lever and the center of gravity, and by Hero's
study of simple machines. They formulated the concept
of “positional gravity” (gravitas secundum situm), with
its implied component forces, and used a principle
analogous to that of virtual displacements or of virtual
work to prove the law of the lever. Gerard of Brussels
was similarly heir to the kinematics of antiquity. In
his De motu he attempted to reduce various possible
curvilinear velocities of lines, surfaces, and solids to
the uniform rectilinear velocity of a moving point. In
the process he anticipated the “mean-speed theorem”
later used by the Mertonians, successfully equating the
varying rotational motion of a circle's radius with a
uniform translational motion of its midpoint.

Other conceptual work in the study of motive pow-
ers and resistances, made in the context of Aristotle's
rules for the comparison of motions, laid the ground-
work for the gradual substitution of the notion of force
(as exemplified by vis insita and vis impressa) for that
of cause, thereby preparing for later more sophisticated
analyses of gravitational and projectile motion.