Text: The Modal Argument and a Berkeleyian World Posted by Soren on 11-26-03 06:43 PM http://forums.philosophyforums.com/printthread.php?t=4586 The following argument was offered as a class handout a few weeks ago. I¹ve been mulling over the argument since then and am curious of your thoughts on the argument. This is NOT my argument. Also, please no ³off the cuff² comments, those were already offered in class and discussed. What I¹m interested in here is serious interaction with the argument. I¹ve got some ideas, but would like some different perspectives . . . Here goes . . . A ³Berkeleyian World² is a world that is as the philosopher George Berkeley conceived it. A world W is Berkeleyian if and only if everything that exists in W is a mind, a state of mind, a quality of mind, or a relation between minds. (Berkeley did not believe in the existence of abstract objects, so strictly speaking, a Berkeleyian world won¹t contain such objects. But if there are abstract objects, then they necessarily exist, and then the notion of a Berkeleyian world will be contradictory, as will the concept of a purely physical world. So, I will construe the notion of a Berkeleyian world here as allowing for there being abstract objects, if there are any. I just won¹t get into that matter further here). Descartes pointed out (as had Greek skeptics before him) that it is logically possible that we have any sensory experience that we have without there being an object that causes or corresponds to it. In other words, (A) For any person S, sensory experience E that S has at time T, and object O that exists at T, if E is veridical or reliable, it is logically possible that S has E at T and O does not exist at T. Descartes (and the skeptics) also noticed that it is logically possible (neither formally nor informally contradictory) that every sensory experience that anyone ever has occur without there being any object that causes or corresponds to any such experience. In other words, (B) For every person S, sensory experience E that S has at time T, and object O that exists at T, if E is veridical or reliable, it is logically possible that S has E at T and O does not exist at T. One need not (invalidly) infer (B) from (A). Each claim stands nicely on its own feet. The point that is relevant here is that, since (A) and (B) are true, our world could be a Berkeleyian world and all of our sensory experience still occur. I¹m not interested here in arguing that our world is Berkeleyian or that it is not. One way of putting the modal argument for the non-identity of mind and body (often called, a bit misleadingly, the modal argument for dualism) begins like this: (1) It is logically possible (neither formally nor informally contradictory) that there be a Berkeleyian world. It is true that: (2) In a Berkeleyian world, minds will exist. (3) In a Berkeleyian world, there will be no bodies. Hence: (4) In a Berkeleyian world, no mind will be identical to any body. (³Any body² of course covers ³anything physical whatever².) Consider, then, our world, whether it is Berkeleyian or not. In it, there are minds where: X is a mind only if X is capable of consciousness and sometimes is conscious. (This states a necessary condition of being a mind, which is sufficient for present purposes.) The modal argument continues: (5) Metaphysical identity is necessary. (6) There are minds in our world. (7) If the minds in our world are identical to bodies, then they are necessarily identical to bodies. (See 5) (8) If the minds in our world are necessarily identical to bodies, then (i) all minds are necessarily identical to bodies, and so (ii) a Berkeleyian world is impossible. (9) It is false that the minds in our world are necessarily identical to bodies. (A Berkeleyian world is not impossible) [from (1) and (8)] (10) The minds in our world are not identical to bodies. [from 7 and 9] Thanks all, Soren

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