most important articles of our knowledge might have remained latent in the mind, even when those occasions presented themselves to which they were immediately applicable.”
Association of ideas depends upon two principles known, respectively, as (1) the law of contiguity; and (2) the law of similarity. Association by contiguity is that form of association by which an idea is linked, connected, or associated with the sensation, thought, or idea immediately preceding it, and that which directly follows it. Each idea, or thought, is a link in a great chain of thought being connected with the preceding link and the succeeding link. Association by similarity is that form of association by which an idea, thought, or sensation is linked, connected, or associated with ideas, thoughts, or sensations of a similar kind, which have occurred previously or subsequently. The first form of association is the relation of sequence—the second the relation of kind.
Association by contiguity is the great law of thought, as well as of memory. As Kay says: “The great law of mental association
