It seems that we can think of anything. We can "form monsters, and join incongruous shapes and appearances" (IP3 106a)

But our thought is "really confined within very narrow limits." (IP3 106a)

"[A]ll this creative power of the mind amounts to no more than the faculty of compounding, transposing, augmenting, or diminishing the materials afforded us by the senses and experience." (IP3 106a)

Materials afforded us by the senses ...:	We've seen dogs, desks, persons, televisions, etc.
Compounding:	We can imagine a dog on top of a desk.
Transposing:	We can imagine a person with arms coming out of his head.
Augmenting:	We can imagine a giant.
Diminishing:	We can imagine a television smaller than a fingernail.

But, Hume says, our powers of imagination end there.

Try to think of an idea that we don't get through "compounding, transposing, augmenting, or diminishing the materials afforded by the senses and experience."