Cartesian dualism relies upon two substances, body and mind, which are totally distinguished by their properties. While the characteristic nature of body is Extendedness, the mind is known with its capability of thinking. So, Cartesian Dualism is founded on these two basic propositions: 1. All bodies are extended. And 2. All minds are thinkable. Abandoning the latter, the former (1) seems acceptable to all physicalists. But if so, then its contraposition might be true equally. In other words, physicalists should be agreed with this proposition too: 3. All non-extended are non-body The question is how physicalists justify this proposition? In other hand, the unavoidable consequence of this proposition (and its truth) is existence of a non-extended (entity) which isn't body, which isn't justifiable in reductive physicalism approach. So, considering this proposition that in reductive physicalism approach: 4. everything has identify with physics. But, isn’t paradoxical acceptance of (3) and (4) together? how physicalists justify the existence of non-extended entities which aren't bodies? Thanks! Borhan S., a student of philosophy of science.

Dear Borhan,

The answer to your question requires some deductive logic. Let's start with (1) all bodies are extended, which is Descartes' premise. It follows logically that if something is not extended, then it is not a body. Thus (3) follows logically from (1). You are worried because you think that (3) assumes that something is not extended. But it does not. It only claims that IF something is non extended then it is also not a body. So physicalists can agree with the claim.

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