Now it is obvious that any mind in which association by similarity is highly developed is a mind which will spontaneously form lists of instances like this. Take a present fact _A_, with a character _m_ in it. The mind may fail at first to notice this character _m_ at all. But if _A_ calls up _C_, _D_, _E_, and _F_,--these being phenomena which resemble _A_ in possessing _m_, but which may not have entered for months into the experience of the animal who now experiences _A_, why, plainly, such association performs the part of the reader's deliberately rapid comparison referred to above, and of the systematic consideration of like cases by the scientific investigator, and may lead to the noticing of _m_ in an abstract way. Certainly this is obvious; and no conclusion is left to us but to assert that, after the few most powerful practical and æsthetic interests, our chief help towards noticing those special characters of phenomena which, when once possessed and named, are used as reasons, class names, essences, or middle terms, _is this association by similarity_. Without it, indeed, the deliberate procedure of the scientific man would be impossible: he could never collect his analogous instances. But it operates of itself in highly-gifted minds without any deliberation, spontaneously collecting analogous instances, uniting in a moment what in nature the whole breadth of space and time keeps separate, and so permitting a perception of identical points in the midst of different circumstances, which minds governed wholly by the law of contiguity could never begin to attain. [Illustration: FIG. 66.] Figure 66 shows this. If _m_, in the present representation _A_, calls up _B_, _C_, _D_, and _E_, which are similar to _A_ in possessing it, and calls them up in rapid succession, then _m_, being associated almost simultaneously with such varying concomitants, will 'roll out' and attract our separate notice. If so much is clear to the reader, he will be willing to admit that the mind _in which this mode of association most prevails_ will, from its better opportunity of extricating characters, be the one most prone to reasoned thinking; whilst, on the other hand, a mind in which we do not detect reasoned thinking will probably be one in which association by contiguity holds almost exclusive sway. Geniuses are, by common consent, considered to differ from ordinary minds by an unusual development of association by similarity. One of Professor Bain's best strokes of work is the exhibition of this truth. It applies to geniuses in the line of reasoning as well as in other lines.