Below I’ve quoted or summarized some ideas developed by Mortimer Adler in his book, The Difference of Man and the Difference it Makes. His thesis: (1) Conceptual thought is an immaterial power and, therefore, the brain is a necessary but not sufficient condition of conceptual thought. (2) If this is not the case, human beings are not radically different in kind from animals but only superficially different in kind based on underlying differences in degree (more powerful brains), and there is no basis to treat animals differently than humans or to object when more intelligent humans subjugate less intelligent humans.
My response to some comments during the discussion:
“[C]oncepts whereby we understand what different kinds or classes of things are like consist in meanings or intentions that are universal.” Id. 220 “[N]othing that exists physically is actually universal; anything that is embodied in matter exists as an individual.” Id. 220-221. “Hence [our concepts] do not exist physically; they are not embodied in matter.” Id. 222. “Since our concepts are acts of our power of conceptual thought, that power must itself be an immaterial power, one not embodied in a physical organ such as the brain.” Id. “The action of the brain . . . cannot be the sufficient condition of conceptual thought, though it may still be a necessary condition thereof.” Id.
“Since, unlike concepts, perceptual abstractions do not have an intentionality that is universal in character, immateriality need not be attributed to the power of which they are acts.” Id. 225.
Two things are different in kind when one has a defining characteristic the other lacks. With a difference in kind, no intermediate object is possible with respect to the property in question (a trait of discontinuity). Two things are different in degree when they have common characteristics, but one has more than the other. With a difference in degree, an intermediate object is always possible (a trait of continuity). Id. 19-35.
A radical difference in kind is rooted in an underlying difference in kind involving a factor present in one but totally absent in the other (An example: odd numbers are not divisible by 2, but even numbers are). A superficial difference in kind is rooted in an underlying difference in degree involving a critical threshold that makes one thing have something another does not (An example: liquid, solid, and gas). Id. 23-27.
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