The Association of Ideas

18. It is evident that there is a principle of connexion between the different thoughts or ideas of the mind, and that, in their appearance to the memory or imagination, they introduce each other with a certain degree of method and regularity. In our more serious thinking or discourse this is so observable that any particular thought, which breaks in upon the regular tract or chain of ideas, is immediately remarked and rejected. And even in our wildest and most wandering reveries, nay in our very dreams, we shall find, if we reflect, that the imagination ran not altogether at adventures, but that there was still a connexion upheld among the different ideas, which succeeded each other. Were the loosest and freest conversation to be transcribed, there would immediately be observed something which connected it in all its transitions. Or where this is wanting, the person who broke the thread of discourse might still inform you, that there had secretly revolved in his mind a succession of thought, which had gradually led him from the subject of conversation. Among different languages, even where we cannot suspect the least connexion or communication, it is found, that the words, expressive of ideas, the most compounded, do yet nearly correspond to each other: a certain proof that the simple ideas, comprehended in the compound ones, were bound together by some universal principle, which had an equal influence on all mankind.

18. Clearly, there is a principle connecting the different thoughts or ideas in our minds. When ideas appear in memory or imagination, they bring other ideas to mind with some order and regularity. In serious thinking or conversation, this pattern is easy to notice. Any thought that interrupts the regular chain of ideas is immediately noticed and rejected. Even in our wildest and most wandering daydreams, and even in our dreams, we can find connections between successive ideas. If we reflect, we will see that the imagination did not wander entirely at random. If the most casual and unrestricted conversation were written down, we would immediately notice something connecting each change of subject. And where such a connection is missing, the person who broke the thread of conversation could still explain it. A series of thoughts had been passing privately through that person’s mind, gradually leading away from the subject. Even languages with no possible connection or contact have words for the most complex ideas that closely correspond. This is certain proof that some universal principle binds the simple ideas within those complex ideas together. The principle has the same influence on all humanity.

19. Though it be too obvious to escape observation, that different ideas are connected together; I do not find that any philosopher has attempted to enumerate or class all the principles of association; a subject, however, that seems worthy of curiosity. To me, there appear to be only three principles of connexion among ideas, namely, Resemblance, Contiguity in time or place, and Cause or Effect.

19. Although it is obvious that different ideas are connected, I know of no philosopher who has listed or classified all the principles of association. Yet this subject seems worth exploring. To me, there seem to be only three principles connecting ideas: Resemblance, Closeness in time or place, and Cause or Effect.

That these principles serve to connect ideas will not, I believe, be much doubted. A picture naturally leads our thoughts to the original²: the mention of one apartment in a building naturally introduces an enquiry or discourse concerning the others³: and if we think of a wound, we can scarcely forbear reflecting on the pain which follows it⁴. But that this enumeration is complete, and that there are no other principles of association except these, may be difficult to prove to the satisfaction of the reader, or even to a man's own satisfaction. All we can do, in such cases, is to run over several instances, and examine carefully the principle which binds the different thoughts to each other, never stopping till we render the principle as general as possible⁵. The more instances we examine, and the more care we employ, the more assurance shall we acquire, that the enumeration, which we form from the whole, is complete and entire.

I believe there can be little doubt that these principles connect ideas. A picture naturally leads our thoughts to the original². Mentioning one room in a building naturally leads us to ask or talk about the others³. And if we think of a wound, we can hardly stop ourselves from thinking about the pain that follows it⁴. But it may be difficult to prove that this list is complete and that there are no other principles of association. It may be difficult to prove this to the reader’s satisfaction, or even to our own. In such cases, all we can do is examine several examples. We must carefully examine the principle that links the different thoughts in each example. We must not stop until we have made the principle as general as possible⁵. The more examples we examine and the more care we take, the more confident we become that our list, drawn from all the examples, is complete.