The mind is continually under the influence of some desire. It constantly has some plan to accomplish, some cause to search out, or some gratification to secure. The present wish or desire of the mind imparts an interest to whatever conception seems calculated to forward this object. Thus, if the mathematician has a problem to solve, and this is the leading desire of the mind, among the various conceptions that arise, those are the most interesting which are fitted to his object, and such immediately become vivid and distinct. If the painter or the poet is laboring to effect some new creation of his art, and has this as the leading object of desire, whatever conceptions seem best fitted to his purpose are immediately invested with interest, and become distinct and clear. If the merchant, or the capitalist, or the statesman has some project which he is toiling to accomplish, whatever conceptions appear adapted to his purpose soon are glowing and defined, in consequence of the interest with which desire thus invests them.
From this it appears that the _chief end_, or leading object of desire of the mind, will in a great measure determine the nature and the succession of its conceptions. If a man has chosen to find his chief happiness in securing power and honor, then those conceptions will be the most interesting to his mind that best fall in with his object. If he has chosen to find happiness in securing the various gratifications of sense, then those conceptions that most coincide with this desire will become prominent. If a man has chosen to find his chief enjoyment in doing the will of God, then his conceptions will, to a great extent, be conformed to this object of desire. The current of a man's thoughts, therefore, becomes the surest mode of determining what is the governing purpose or leading desire of the mind.
But there are seasons in our mental history when the mind does not seem to be under the influence of any governing desire; when it seems to relax, and its thoughts appear to flow on without any regulating principle. At such times the vividness of leading conceptions, which otherwise is determined by _desire_, seems to depend upon our past experience. Those objects which, in past experience, have been _associated with emotion_, are those which thus begin to glow in the distinct lineaments with which emotion at first invested them.