Those who, like Professor Ryle, revolt against a dichotomy to which
they have been once addicted, commonly go over to maintain that only
one of the alleged pair of opposites really exists at all. And so he, though
he does not believe the body is a machine, does believe that it alone,
and not the “ghost,” exists: he preaches with the fervour of a proselyte a
doctrine of “one world.” Yet what has ever been gained by this favourite
philosophical pastime of counting worlds? And why does the answer
always turn out to be one or two, or some similar small, well-rounded
philosophically acceptable number? Why, if there are nineteen of anything, is it not philosophy?
This reminds me of the computer scientist’s dictum that for any resource, there should either be zero, one, or an infinite number of it. But since 95 percent (my own estimate) of engineering is dealing with resource constraints, it’s more of a theoretical rule rather than a practical one. But we all want the universe to reduce to theory, right?
The Greeks seem to have been immune to this, though; see Plato (mis-)counting the 729 multiplier of happiness, or (as pointed out by Avrum Stroll) Aristotle counting up the 47 or 55 unmovable substances.
Update: Following on from comments, I have to quote this:
[at the edge of the universe, Fry sees alternative versions of himself and his friends on the other side]
Fry: So there is an infinite number of universes.
Professor Hubert Farnsworth: No, just the two.
Fry: Oh, well. I guess that’s enough.