A mental property is a property of the mind. For example, if someone pricks you with a pin, you will most likely feel pain. That instance of feeling pain is an instantiation of the property being in (or a) pain.
It is important to distinguish between the predicate 'is a pain' which is a linguistic entity, and the property denoted by the predicate. This becomes important in the philosophy of mind when the two are confused, especially concerning intertheoretic reductionism and ontological reductionism.
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