Sofia asked:

"If X might exist but we have no reason to suppose that it actually does exist, then as metaphysicians
we should not concern ourselves with X." Is this true? Why or why not?

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Good question. I'd say that the sentence is false. David Chalmers recently wrote a book on the nature
of consciousness. In that book he spends much time talking about 'zombies'. A zombie is a creature
who is physically identical to you but lacks your conscious experience. Now, Chalmers would
probably say that there is little reason to suppose that the actual world has zombie inhabitants. But
that fact that zombies could exist tells us some interesting things about metaphysical nature of
consciousness (i.e. that consciousness cant be a purely physical thing because something can be
physically identical to you be lack all conscious experience). So, zombies might exist, they don't
actually exist, but the argument goes that the fact that they exist in some possible, but non-actual,
world means that they can still tell the metaphysician some very interesting (and controversial!) things
about the nature of mind. The interesting thing is that when metaphysicians talk about things that
might exist but don't actually exist, they usually means that there exists a possible world and at that
world that thing does exist. The nature of possible worlds is of course a matter of great controversy. I
wrote a couple of answers about them in the past so you might want to look there. Feel free to email
me with any questions....

Hope that helped.

Rich Woodward