Indeed, there are few objects, either of perception or conception, which, however close the process of abstraction, do not remain complex in their nature. The simplest forms of matter are combined ideas of extension, figure, color, and relation. These different ideas we gain by the aid of the different senses. Of course, our conceptions are combinations of different qualities in an object which the mind considers as one, and as distinct from other objects.
Each item, then, in any mental picture is itself a complex object, and each mental picture is formed by a combination of such complex objects. It will be found very difficult, if not impossible, to mention a name which recalls any object of sense in which the conception recalled by the word is a single disconnected thing, without any idea of place or any attendant circumstances, and, as before remarked, almost all objects of sense are complex objects, combining several ideas, which were gained through the instrumentality of different senses. The idea of color is gained by one sense, of position, shape, and consistency by another, and other qualities and powers which the mind associates with it by other senses.
The other fact necessary to the correct understanding of the subject is the influence which the desires and emotions have upon the character both of the perceptions and conceptions with which they coexist.
It will be found that our sensations vary in vividness and distinctness according to the strength and permanency of certain feelings of desire which coexist with them. For example, we are continually hearing a multitude of sounds, but in respect to many of them, as we feel no desire to know the cause or nature of them, these sensations are so feeble and indistinct as scarcely ever to be recalled to the mind or recognized by any act of memory; but should we hear some strange wailing sound, immediately the desire would arise to ascertain its nature and cause. It would immediately become an object of distinct and vivid perception, and continue so as long as the desire lasted.
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 continues to learn the cause of that strange wailing sound, the other sensations would all be faint and indistinct. When this desire is gratified, then other sensations would 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 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.
But now the mind possesses the power of abstracting a greater or fewer number of qualities, and to these qualities a name is given, and whenever these qualities are found combined in any object, this name can be applied. Thus the name animal is given to any thing which has the qualities of existence and animal life, and the name quadruped is given to any object which has the qualities of animal life and of four legs.