Connection of Ideas

In book three Hume talks a good deal about the connection that exists between all ideas. Hume talks about three principles by which ideas may be connected. The first principle he talks about is resemblance, this is where we see a picture of a tree and we then think about the tree. The second principle he talks about is contiguity of time and place, this is where if we are to mention one apartment we then get to discussing others. The last principle he talks about is cause and effect, where when we think of a cut or scrape and then we think about the pain that followed it. Hume then goes on to say that he has no reason to not put out more prinicples for the connection of ideas, expect for the fact that he can not come up with anymore. Though he does then say that even though he can't think of anymore no more are needed. For example, association by means of contrast or contrariety can be seen as a combination of resemblance and causation.