Argument from queerness

"The Argument from Queerness" is a term used by J. L. Mackie in his book Ethics: Inventing Right and Wrong to describe a certain sort of reductio ad absurdum that he uses against moral objectivism; he argues that "if there were objective values, then they would be entities of a very strange sort, utterly different from anything else in the universe", and that this in itself is sufficient reason for doubting their existence. The same sort of argument could be applied to other supposed unperceivable entities, such as a God or gods, a soul or "self" or free will.

Criticisms of the argument include noting that for the very fact that such entities would have to be something fundamentally different from what we normally experience - and therefore assumably outside our sphere of experience - we cannot prima facie have reason to either doubt or affirm their existence; therefore, if one had independent grounds for supposing such things to exist (such as, for instance, a reductio ad absurdum of the contrary) then the argument from queerness cannot give you any particular reason to think otherwise.