Association is of two kinds. For, on the one hand, it may be a natural disposition, which was from birth destined to develop itself whatever the child’s outward experiences might be, so long as he was not maimed nor virtually maimed, say by being imprisoned. This sort of association by virtue of which certain kinds of ideas become naturally allied, as crimson and scarlet, is called association by resemblance. The name is not a good one, since it implies that the resemblance causes the association, while in point of fact it is the association which constitutes the resemblance. In themselves considered any two sense-qualities are what they are to themselves alone and have no relation to one another. But could they be compared by a mind that brought no tinge of its own nature into the comparison, any two ideas would appear somewhat alike and somewhat different. But the human mind attaches a peculiar value and emphasis to some resemblances, and that consists in this, that when one quality is brought vividly to consciousness, others will at once have their vividness increased, some more, some less. Thus, an idea which may be roughly compared to a composite photograph surges up into vividness, and this composite idea may be called a general idea. It is not properly a conception; because a conception is not an idea at all, but a habit. But the repeated occurrence of a general idea and the experience of its utility, results in the formation or strengthening of that habit which is the conception; or if the conception is already a habit thoroughly compacted, the general idea is the mark of the habit.