In philosophical terms, an analogy is a comparison between two objects or two categories of objects. For example, one can form an analogy between a school and a hospital, since they are both institutional buildings.

For David Hume, a belief is simply a particularly vivid idea (237), although he admits that he is not certain how a belief becomes distinct from other ideas.

Hume defines a cause as an idea that is closely related to another (220), like heat being related to a flame.