I wish to prove to you that there exists a unicorn.

To do this, it obviously suffices to prove the (possibly) stronger statement that there exists an existing unicorn. (By an existing unicorn I of course mean a unicorn which exists.) Surely if there exists an existing unicorn, then there must exist a unicorn.

So all I have to do is prove that an existing unicorn exists.

Well, there are exactly two possibilities:

(1) An existing unicorn exists.Possibility (2) is clearly contradictory: How could an existing unicorn not exist? Just as it is true that a blue unicorn is necessarily blue, an existing unicorn must necessarily be existing.

(2) An existing unicorn does not exist.

From Raymond Smullyan, *What is the Name of this Book?* (1978).

Achilles & the tortoise

The surprise exam

Newcomb’s problem

Newcomb’s problem (sassy version)

Seeing and being

Logic test!

Philosophers say the strangest things

Favourite puzzles

Books on consciousness

Philosophy videos

Phinteresting

Philosopher biographies

Philosopher birthdays

Draft

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