Thursday, August 17, 2017

Angus Menuge responds to Keith Parsons

This part is incomprehensible to me:

It is not the abstract propositional content of, say, the statement of modus tollens that constrains or compels me to reason in accordance with that rule, but rather my physical act of recognition that modus tollens is a valid argument form that, in complex combination with other causal factors and conditions, determines my conclusion in accordance with that rule.

If my recognition of X leads me to do A, then we need an account of how it is that one recognizes X.  Like William Hasker, I find it unintelligible that someone properly trained in logic can derive a conclusion knowing it to be an instance of modus tollens without interacting with modus tollens itself.  But modus tollens is an abstract entity which cannot be reduced to the material world, because of its universality and necessity (Thomas Nagel realizes this).  To see that the conclusion follows as a result of a valid rule of reasoning is to see that it must be true in all possible worlds, a must that can never be justified by the contingent past material interactions of brains (either an individual’s or the whole human species') with their environments.  So our knowledge of logic is not materialistically possible knowledge, hence materialism is false.

This is one of the things I argue in “Knowledge of Abstract: A Challenge to Materialism” (attached), which is, really an example of the argument from reason and fits well, I think, with your whole approach.



Dr. Angus Menuge

1 comment:

David Brightly said...

I can't make sense of what Keith P says here, either. But then nor can I make sense of Angus M's objection. What could possibly count as 'interacting with modus ponens'? The only thing this could be is using if p then q pattern sentences to draw conclusions. This is part of understanding the meaning of if...then... and I could do this several decades before I heard of possible worlds.

I think an important distinction here is between the ability to use modus ponens and the ability to reflect coherently on its logical significance. Angus is raising the hoop way too high for a materialistic understanding of a ten year old child. Maybe not for a thirty year old adult.