At this point in the chain of statements, the classical error of reductionism often makes its entrance, via the following argument: If our brain’s unique capacities arise from its material substrate, and if that substrate originated through ordinary evolutionary processes, then those unique capacities must be explainable by (reducible to) “biology” (or some other chosen category expressing standard scientific principles and procedures).
The primary fallacy of this argument has been recognized from the inception of this hoary debate. “Arising from” does not mean “reducible to,” for all the reasons embodied in the old cliche that a whole can be more than the sum of its parts. To employ the technical parlance of two fields, philosophy describes this principle by the concept of “emergence*,” while science speaks of “nonlinear” or “nonadditive” interaction. In terms of building materials, a new entity may contain nothing beyond its constituent parts, each one of fully known composition and operation. But if, in forming the new entity, these constituent parts interact in a “nonlinear” fashion—that is, if the combined action of any two parts in the new entity yields something other than the sum of the effect of part one acting alone plus the effect of part two acting alone—then the new entity exhibits “emergent” properties that cannot be explained by the simple summation of the parts in question. Any new entity that has emergent properties—and I can’t imagine anything very complex without such features—cannot, in principle, be explained by (reduced to) the structure and function of its building blocks.
— Stephen Jay Gould, In Gratuitous Battle
* A note he qualifies his use of “emergence”:
Please note that this definition of “emergence” includes no statement about the mystical, the ineffable, the unknowable, the spiritual, or the like—although the confusion of such a humdrum concept as nonlinearity with this familiar hit parade has long acted as the chief impediment to scientific understanding and acceptance of such a straightforward and commonsensical phenomenon. When I argue that the behavior of a particular mammal can’t be explained by its genes, or even as the simple sum of its genes plus its environment of upbringing, I am not saying that behavior can’t be approached or understood scientifically. I am merely pointing out that any full understanding must consider the organism at its own level, as a product of massively nonlinear interaction among its genes and environments. (When you grasp this principle, you will immediately understand why such pseudosophisticated statements as the following are not even wrong, but merely nonsensical: “I’m not a naive biological determinist. I know that intelligence represents an interaction of genes and environment—and I hear that the relative weights are about 40 percent genes and 60 percent environment.”)