y and to make its
terminology explicit at this point.[17]

[17] The background for much of the following was derived
from Annaliese Maier, _An der Grenze von Scholastik und
Naturwissenchaft_, ed 2, Rome, 1952.

In scholastic philosophy, all beings and substances are a coalescence
of inchoate matter and enacting form. Form is that which gives being
to matter and which is responsible for the "virtus" or power to cause
change, since matter in itself is inert. Moreover, forms can be
grasped intellectually, whence the nature of a being or a substance
can be known. Any explanation of phenomena has to be based upon these
innate natures, for only if the nature of a substance is known can
its properties be understood. Inanimate natures are determined by
observation, abstraction, and induction, or by classification.[18]

[18] St. Thomas' epistemology for the natural inanimate world
was based upon Aristotle's dictum: that which is in the mind
was in the senses first.

The nature of a substance is causally prior to its properties; while
the definition of the nature is logically prior to these properties.
Thus, what we call the theory of a substance is expressed in its
definition, and its properties can be deduced from this definition.

The world of St. Thomas is not a static one, but one of the
Aristotelian motions of quantity (change of size), of quality
(alteration), and of place (locomotion). Another kind of change is
that of substance, called generation and corruption, but this is a
mutation, occurring instantly, rather than a motion, that requires
time. In mutation the essential nature is replaced by a new
substantial form.

All these changes are motivated by a causal hierarchy that extends
from the First Cause, the "Dator Formarum," or Creator, to separate
intellectual substances that may be angels or demons, to the celestial
bodies that are the "generantia" of the substantial forms of the
elements and finally to the four prime qualities (dry and wet, hot and
cold) of the substantial forms. Accidental forms are motivated by the
substantial forms through the instrumentality of the four prime
qualities, which can only act by material contact.

The only causal agents in this hierarchy that are learned through the
senses are the tangible qualities. Usually the prime qualities are not
observed directly, but only other qualities compounded of them. One of
the problems of scholastic philosophy was th