I have been trying to poke a hole in the following apparently naive argument against materialism/physicalism:
The main justification for materialism is that a person doesn't believe in that which doesn't have observable or measurable properties. Hence a materialist doesn't believe in supernatural beings or separate mental substances. And yet for there to be observation in the first place, there has to be perception, and perception is by definition a mental process. The very starting point of the materialist position is a mental event, and the position that "I only believe in that which I can observe" can lead at best (from the materialist viewpoint) to a Kantian Phenomena/Noumena dualism, and at worst to a Berkeleyan "all is in the mind" idealism. Hence materialism refutes itself by the very fact that it requires an idealist starting point.
How can one refute this argument? And how do materialists deal with perception as an event? (Not perception as qualia, but perception as the transition event from an object being just a material substance to being mental sense data?)