Artists and their audiences entertain hypothetical worlds in the theater of the imagination.

Here are two theatrical performances that demonstrate a more obvious use of imagination. It not only takes imagination to come up with the ideas, but imagination to accept and enjoy them.
On the left is "Jellicle Cats" from Andrew Lloyd Weber's musical "Cats" and on the right is the French mime artist Marcel Marceau.

Imagination is a forerunner of investigation; and investigation furnishes an impetus to imagination. For this reason a great thinker, whether a poet or a philosopher, although he will incline to the one method or to the other, according to the bent of his genius, must not be wholly deficient in the qualities that go to make up either...A vigorous power of representation is as indispensable a condition of success in the abstract sciences as in the poetical and plastic arts..."
(from Imagination and Art)