Review of Book I -- Thomas Aquinas -- Commentary on Aristotle's Metaphysics

In Book I of Commentary on Aristotle's Metaphysics, Aquinas (following Aristotle's text) provides an overview of the beginnings of philosophy. He covers the various views of early philosophers regarding what is the "principle of all things." Additionally, Aquinas comments and expands on Aristotle's critique of Plato's theory of Ideas or Forms.

Aquinas remarks on the ideas of Thales (620-546 B.C.), who held that "water is the first principle of all things." He also mentions Diogenes (5th century B.C.) and Anaximenes (5th century B.C.), "who held that air is the principle of things." Furthermore, he considers the ideas of Empedocles (494-424 B.C.), who maintained that air, fire, water, and earth "are the principles of things." Anaxagoras (510-428 B.C.) agreed with Empedocles, "but also claimed that all things having like parts, such as flesh, bones, marrow and so forth, whose smallest parts are infinite in number, are the principles of things."

Following a discussion of these philosophers, Aquinas begins to address early thoughts on the idea of first cause in philosophy. Parmenides (5th century B.C.) came the closest in arguing that "there are many causes, one of which would be a mover and the others something moved."

Before addressing Plato, Aquinas continues his commentary on Aristotle to discuss the ideas of Pythagoras (570-495 B.C.). The Pythagoreans "thought that the principles of numbers are the principle of all existing things, and they said that the whole heaven is merely a kind of nature and harmony of numbers." In keeping with this, Aristotle remarks that the Pythagoreans held that "the bodies which move in the heavens are ten in number; but as only nine are observable they therefore invented a tenth, the counter-earth."

In the concluding portions of Book I, Aquinas reiterates and elaborates on Aristotle's critique of Plato's theory of Ideas or Forms. Plato argued that what we perceive in reality is only a copy of a form or ideal existing in an eternal realm. Aristotle argued against this idea as an unnecessary layer of abstraction and one that didn't logically follow philosophically.

Aquinas agrees with Aristotle in rejecting Plato's idea of the Forms. However, in place of Plato's forms existing in an eternal realm, Aquinas argues the following:

"God's knowledge is the exemplar of all things. For since things in the physical world are naturally inclined to induce their likeness in things which are generated, this inclination must be traced back to some directing principle which ordains each thing to its end. This can only be the intellect of that being who knows the end and the relationship of things to the end."

Book I also introduces one of the most challenging questions in philosophy or that of innate knowledge we are born with versus acquired knowledge we learn. It appears that Plato held to the idea of innate knowledge. Aristotle and Aquinas rejected this and argued in favor of a person "comes to know, but only of certain other things through which he becomes instructed." Acquired knowledge makes sense in terms of a body of knowledge, but innate knowledge seems more reasonable from a sense of right from wrong. Perhaps Aquinas addresses this elsewhere in his writings.