Aquinas on Matter and Form and the Elements.
Massie, Pascal
BOBIK, Joseph. Aquinas on Matter and Form and the Elements. Notre
Dame: University of Notre Dame Press, 1998. xviii + 325 pp. Cloth,
$39.00; paper, $19.00--This book offers a translation of Aquinas's
De Principiis Naturae (circa 1252) and De Mixione Elementorum (1273)
accompanied by a continuous commentary, followed by two essays:
"Elements in the Composition of Physical Substances" (part 3),
and "The Elements in Aquinas and the Elements Today" (part 4).
The unity of the volume rests in the question of the composition of
natural things (whether out of matter and form, or out of the elements).
The object of the De Principiis Naturae is to account for
generation, that is, the process through which all natural things are
brought into existence. Aquinas identifies three principles: matter,
form, and privation. Form, the actuality of matter, is a per se
principle that is found only in the terminus ad quem of generation. As
such, it is a differentiating principle which, as Bobik rightly insists,
must be distinguished from the "essence," for "whereas
the substantial form differentiates the end term of a radical change
from the beginning term, the essence differentiates the end term from
nothingness" (p. 229). It is not the form itself which has
existence, it is the composite which exists "through the form"
(p. 232). A form never comes to be as a subsisting thing but only as
that by which the subsisting thing subsists. Forms are
"educed" (eductae) from the potency of the elements into the
actuality of the composite. Eduction (by contrast with generation or
creation), designates the potentiality of already informed matter to
receive a new substantial form. Matter and privation on the other hand
are found together in the terminus a quo, for what can be (matter) is
not what it can become (privation). Privation (a principle per accidens)
is not, however, mere nothingness (otherwise we would have creation, not
generation) but determinate nonbeing; the nonbeing of that which is in
potency, or as Bobik puts it: "a non-being which is as well as a
being which is not" (p. 23). This is why the matter which is found
together with privation cannot be prime matter but determinate elemental
matter. Finally, privation leads Aquinas to distinguish principles from
causes along the distinction of generation and existence. Form and
matter are both principles and causes because both are intrinsic causes
of the "existing" substance. Yet whereas all causes are
principles, all principles are not causes, for privation does not
account for the existence but for the "coming to be" of
substance.
The De Mixione answers the question "how do elements remain in
a mixed body?" (p. 103). Elements are natural bodies indivisible into species diverse from their own. As such they are not only material
but also efficient causes. The elements cannot remain with their
substantial form in a mixed body, for otherwise such a body would rather
be a juxtaposition of substances. Since a mixed body differs in kind
from its constituents, it must have a substantial form of its own.
Aquinas's resolution is that the elements remain with respect to
power, not with respect to their forms. A complex body is a mixio in
which the qualities of the elements affect and alter each other so as to
remain virtually (that is, as retrievable powers) but not actually
(without a corresponding substantial form).
In part 4, Bobik draws a parallel with modern physics. For a time,
modern physics was thought of as atomistic, thus unable to accept the
idea of mixio as Aristotle and Aquinas understood it. In a chemical
combination for instance, the elements were thought to remain intact at
the atomic level. This view is now challenged, however, and science must
make room for a conception of both the elements and the mixed bodies.
The quarks which survive in a proton do not retain their substantial
form; "they have been corrupted with respect to what they actually
are, as determined by their substantial forms. But they have not been
corrupted with respect to what they can actually do, i.e. with respect
to their powers" (p. 275). Further, Bobik proposes an analogy
between the concept of prima materia and neutrinos (the electron
neutrino is understood as having no electric charge, no strong force, no
spatial extent, no electromagnetic force, and possibly no mass).
This volume demonstrates (against a common misrepresentation) that
(1) hylemorphic composition is not to be understood as a juxtaposition
of preexisting and unrelated principles (matter and form) but that (2)
hylemorphism can account for the unity of natural substances, and (3)
reconcile this unity with the reality of the autonomous movement of
nature toward its end. Bobik's translation is remarkably clear and
it is only unfortunate that the commentary limits itself for the most
part to a repetitive paraphrase.
--Pascal Massie, Vanderbilt University.
