[By Alex Gregory]
One hair on your chin does not make a beard.
If you do not have a beard, growing one additional hair will not give you a beard.
Conclusion: No-one have ever grown a beard.
That's Sorites paradox. Some predicates are vague; it isn't clear where they start and end. Still, we want to maintain, the predicates do still apply: Some people are bearded, some are not, regardless of whether there's a murky uncertainty in the center of the scale. That's why its called Sorites paradox: it's hard to square the above argument with our deep conviction that some people really are bearded.
It might be the case that in some cases of this form, we really do conclude that the predicate in question in not "real". But hopefully the above shows that the mere fact of vagueness is not sufficient to draw the conclusion that the predicate is not real.
So here are two other arguments which I think are secretely of this form I've heard from time to time:
There aren't really "black" or "white" people, because it's really only a scale between various skin colours
There aren't really "heterosexual" or "homosexual" people, everyone is really some degree of bisexual.
In both cases, I think we need more evidence to draw the supposed conclusion. Again, the mere fact of vagueness need not propel us into thinking that the terms in question are not real.
Does anyone think that there really is some additional evidence available in support of the conclusions above?
Can anyone name an argument of this form that we do seem to take at face value to show that the predicate in question is not real?