Channeling Gaunilon

Via Bill Vallicella. My take on this -- to live up to the blogosphere's tradition of commenting on things you don't fully understand -- is that it's not clear to me why the fact that we can imagine something being true of A but not of B entails that A and B cannot be identical. Take someone who thinks the evening star and the morning star are two different entities rather than the same thing (namely, the planet Venus). That person could then make claims that are true of the evening star which are not (so he thinks) true of the morning star. "The evening star changed color or blew up" or whatever, "but the morning star remains the same as it always has." In other words, the fact that you can imagine something applying to the one without applying to the other could mean nothing more than that you've misidentified one thing as two. However, this may not apply to Plantinga's argument, since the evening/morning star is an object, and the individual is a subject; and it is precisely as subject that the apparent distinction between it and the body arises.

It looks to me that this modal argument shares a similar intuition with the Ontological Argument: if we can imagine X, then that imagining shows the actual possibility of X. As such, it seems to be subject to the common objection to the Ontological Argument: just because I can imagine X, it doesn't mean that X is actual, and X's actuality is necessary in order for the argument to hold. The counter-response in both cases is that the case under question has a particular quality such that such an imagining does entail its actuality. I tend to agree with Bertrand Russell, that Ontological Arguments are easily dismissed, but it's much harder to explain exactly what's wrong with them. Since Plantinga is one of the most prestigious contemporary defenders of the Ontological Argument, I suspect he might have a better grasp on this than I do.

(cross-posted at Quodlibeta)