While one sensation becomes thus clear and prominent, it will be found that other sensations which were coexisting with it will become feebler and seem to die away. The same impressions may still be made upon the eye as before, the same sounds that had previously been regarded may still strike upon the ear, but while the desire to learn the cause of that strange wailing sound continues, the other sensations will all be faint and indistinct. When this desire is gratified, then other sensations resume their former distinctness and prominency. Our _conceptions_, in like manner, are affected by the coexistence of emotion or desire. If, for example, we are employing ourselves in study or mental speculations, the vividness of our conceptions will vary in exact proportion to the interest we feel in securing the object about which our conceptions are employed. If we feel but little interest in the subject of our speculations, every conception connected with them will be undefined and indistinct; but if the desire of approbation, or the admonitions of conscience, or the hope of securing some future good stimulate desire, immediately our conceptions grow more vivid and clear, and the object at which we aim is more readily and speedily secured. 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.