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 great art, then, of quickening mental vigor and activity, and of gaining clear and quick conceptions, is to awaken interest and excite desire. When this is secured, conceptions will immediately become bright and clear, and all mental operations will be carried forward with facility and speed. The distinction between _attention_ and _abstraction_ is not great, but, as it is recognized in language, it needs to be definitely understood. _Attention_ has been defined as "the direction of the mind to some particular object, from the interest which is felt in that object." It consists simply in a feeling of desire coexisting with our sensations and conceptions, and thus rendering them vivid and distinct; while, in consequence of this fact, all other sensations and conceptions seem to fade and grow indistinct. Attention seems to be the generic exercise, and abstraction one species of the same thing. Attention is used to express the interest which attends our perceptions or conceptions as _whole objects_, thus rendering them clear and distinct from other surrounding objects. Abstraction is that particular act of attention which makes _one part_ or _one quality_ of a complex object become vivid and distinct, while other parts and qualities grow faint and indistinct. Thus, in viewing a landscape, we should be said to exercise the power of attention if we noticed some object, such as a stream or a bridge, while other objects were more slightly regarded; and we should exercise the power of abstraction if we noticed the _color_ of the bridge or the _width_ of the stream, while their other qualities were not equally regarded. It is the power of abstraction which is the foundation of _language_ in its present use. Were it not for the power which the mind has of abstracting certain qualities and circumstances of things, and considering them as separate and distinct from all other parts and qualities, no words could be used except such as specify particular individuals. Every object that meets our eye would demand a separate and peculiar name, thus making the acquisition of language the labor of a life.