Within the genus of (philosophical) relations, Hume distinguishes a species of ‘natural’ relations: resemblance, contiguity in time and place, and causation. His doctrine of the association of ideas involves causation: an idea will be apt to cause the mind to have another idea that relates in a certain way to the first idea. Complexities within this doctrine are teased apart. Hume's extremely strange section entitled ‘Knowledge’, in which he theorizes about seven kinds of relations, is explained.
Keywords: association, Hume, idea, relations