The third view, advanced by Aristotle, attempted to correct what he thought to be the errors in the two extreme views. In his conception of human nature, man is neither just a body or a collocation of atoms nor a union of two quite distinct and separable substances, one material and the other spiritual – one a body and the other a rational soul or mind.
In Aristotle’s view, man is a single substance and, in that respect, is like every other individual thing in the physical cosmos. However, unlike every other corporeal substance, man, as a single substance, is composite of matter and spirit, of material and immaterial aspects – the immaterial aspect consisting in the intellectual power that distinguishes man from other animals.
According to this third view, man is neither entirely a material thing, composed of elementary particles of matter or quanta of energy, nor is he compounded of two substances as alien to one another as body and soul or matter and mind. He is a living organism like any other animal, but he is distinguished from all other animals by virtue of having a mind or intellect – the powers and operation of which cannot be explained by the action of the brain.
Brain action is a necessary, but not a sufficient, condition for the occurrence of mental operations or processes. There is, in short, something immaterial about man, something spiritual in the sense that it is not reducible to bodily parts or movements and not explicable entirely by reference to them.
Mortimer J. Adler – The Angels and Us p.148
As Aristotle noted long ago, thought – or speech or reason – itself moves nothing, especially, one can add, thought merely laid down next to appetite. Thought, to be effective, must be inseparable from appetite.
The true source of action is not abstract thought, nor even thought applied to some separate motor or motive force, but rather a concretion, a grown-togetherness, of appetite and mind, so intertwined that one cannot say for sure whether the human principle of action is a species of desire become thoughtful, or an activity of intellection suffused with appetite. How mind and desire become grown together is, of course, a great question, but it is rarely accomplished by applying purely rational doctrines or rules in a passionless way to human agents. On the contrary, the true beginning is rather with the direct but unreflective education of our loves and hates, our pleasure and pains, gained only in practice, through habituation and by means of praise and blame, reward and punishment. Anyone concerned with influencing conduct must be concerned with these in-between powers of the soul, themselves irrational (in the sense of nonreasoning) but fully amenable to reason (in the sense of being formed, to begin with, in accordance with the reasons of one’s parents, teachers and laws, and being open to further refinement through the exercise of one’s own powers of deliberation and discernment).
Leon R. Kass – Life, Liberty, and the Defense of Dignity: The Challenge for Bioethics p.68
Aristotle claimed that to deny metaphysics is to do metaphysics. We have seen some reason to agree with Aristotle. The arguments against metaphysics, whether Anti-Realist, Lightweight Realist, Skeptical, or Fictionalist, are all based on certain conceptions about truth, meaning, knowledge, and explanation that inevitably raise metaphysical questions.
Robert C. Koons & Timothy H. Pickavance – Metaphysics: The Fundamentals p.241