Darwin follows up with objections raised. Most of these are quite uninteresting and are literally arguments against certain bird specialists. He does make one interesting comment in passing (chapter 7).
“Lastly, more than one writer has asked, why have some animals had their mental powers more highly developed than others, as such would be advantageous to all” (106)?
This anticipates Plantinga’s “Evolutionary Argument Against Naturalism.” If I don’t have a mind or soul, nor have I freedom, this means that everything I do is causally determined by events, circumstances, and neurons firing. This means either (a) beliefs themselves are physical states (remember, on Darwin’s reading there is no soul) or (b) are reduced to physical states. If that’s the case, in order to survive I don’t need to believe in (x), I just need to react vis-a-vis my nervous system. If naturalism is true, then why should I believe it to be true?
Here is the problem: beliefs are true or false. Physical states (or events) are not. They are either accurate or inaccurate.
Of course Darwin doesn’t mention any of that, nor do his critics. I think the reality and presupposition of the soul was still dominant that there was no point.
Later in the chapter Darwin mentions of a certain species’s “Powers of movement” (115). I find it interesting that he is still using Aristotelian language.
Chapter 8: Instinct
Most of this chapter is a reflection on the relationship between instinct and habit. Nothing major hinges on it. The only possible problem arises when we get to categories like “dispositions” and the like. These aren’t physical states. They are mental states.