The same doctrine leads to some cur..

conclusions with respect to vision. Suppose the eye to be fixed in a particular position, and the picture of an object to be painted on the retina. Does the mind perceive the complete figure of the object at once, or is this perception the result of the various perceptions we have of the different points in the outline? With respect to this question, the principles already stated lead me to conclude, that the mind does, at one and the same time, perceive every point in the outline of the object, (provided the whole of it be painted on the retina at the same instant ;) for perception, like consciousness, is an involuntary operation. As no two points, however, of the outline are in the same direction, every point, by itself, constitutes just as distinct an object of attention to the mind, as if it were separated by an interval of empty space from all the rest. If the doctrine, therefore, formerly stated be just, it is impossible for the mind to attend to more than one of these points at once; and as the perception of the figure of the object implies a knowledge of the relative situation of the different points with respect to each other, we must conclude that the perception of figure by the eye is the result of a number of different acts of attention. These acts of attention, however, are performed with such rapidity, that the effect, with respect to us, is the same as if the perception were instantaneous.

In further confirmation of this reasoning, it may be remarked, that if the perception of visible figure were an immediate consequence of the picture on the retina, we should have, at the first glance, as distinct an idea of a figure of a thousand sides, as of a triangle or a square. The truth is, that when the figure is very simple, the process of the mind is so rapid, that the perception seems to be instantaneous; but when the sides are multiplied beyond a certain number, the interval of time necessary for these different acts of attention becomes perceptible.

It may perhaps be asked, what I mean by a point in the outline of a figure, and what it is that constitutes this point one object of attention? The answer, I apprehend, is, that this point

is the minimum visibile. If the point be less, we cannot perceive it; if it be greater, it is not all seen in one direction.

If these observations be admitted, it will follow, that, without the faculty of memory, we could have had no perception of visible figure.*

* I have been accused of overlooking, in the preceding Chapter, a very important distinction between Voluntary and Involuntary attention. In some cases, (it is said,) attention attaches itself spontaneously to its object. In others, it requires a painful effort to keep it steady, nay, when we will to fix it on one subject, we find it perpetually wandering to another. The fact on which the criticism is founded must unquestionably be admitted, but the conclusion drawn from it is nevertheless erroneous. It proceeds on a vague use of the words voluntary and involuntary. These words, as well as the substantive will, are often, but very inaccurately, employed to express a general purpose or intention, as well as that state of mind which is the immediate antecedent of action. Thus, if I resolve to keep my eyes steadily open, I may, according to common modes of speech, be said to will to keep them open, and if in consequence of some sudden alarm, I should depart from my purpose, the winking of my eyelids may be said to be involuntary. And yet, in strict philosophical propriety, the winking of my eyelids is an act purely voluntary; an operation which I will to perform, in consequence of the effect which my alarm has to banish my general purpose or resolution from my mind. The case is perfectly parallel with respect to attention. When I am anxious to attend to a particular subject, I am apt to say that I will to attend to it, and when I forget my purpose, that my inattention is involuntary; whereas the fact is, that the unintended distraction, like the unintended winking of the eyelids, was the effect of a particular volition of the mind, exerted in consequence of a momentary forgetfulness of my general purpose. Indeed, to those who are at all accustomed to precision in the use of language, the phrase involuntary attention must appear a manifest contradiction in terms.

[Stewart is mistaken in supposing that the winking of the eyelids is always, or even generally, a voluntary act. Physiologists are now agreed that, most frequently, it is as involuntary as sneezing, or coughing from irritation of the larynx. Recent discoveries have established the existence of what is called the reflex action of the nerves, by which, without any sensation being communicated to the brain, and consequently without any effort of the will, an impression made upon the end of a nerve is transmitted to the spinal cord, and thence sent back again, as it were, along one of the motor nerves to its extremity, producing there a contraction of the nerves and the requisite movement of the limb or organ. Isolate this pair of nerves entirely, by cutting off its communication, not only with the head, or de the

CHAPTER III.

OF CONCEPTION.

Office of Conception.- By conception, I mean that power of the mind, which enables it to form a notion of an absent object of perception; or of a sensation which it has formerly felt. I do not contend that this is exclusively the proper meaning of the word, but I think that the faculty which I have now defined, deserves to be distinguished by an appropriated name.

When a

Conception is often confounded with other powers. painter makes a picture of a friend, who is absent or dead, he is commonly said to paint from memory; and the expression is sufficiently correct for common conversation. But in an analysis of the mind, there is ground for a distinction. The power of conception enables him to make the features of his friend an object of thought, so as to copy the resemblance; the power of memory recognizes these features as a former object of perception. Every act of memory includes an idea of the past; conception implies no idea of time whatever.*

According to this view of the matter, the word conception corresponds to what was called by the schoolmen simple apprehension; with this difference only, that they included, under this name, our apprehension of general propositions; whereas I

but with the upper and lower portions of the spinal column, reserving only a segment of this column to connect the excitor with the motor nerve, and the reflex movement may still be produced. Thus, when the mucous membrane of the nose is irritated, sneezing follows in spite of any effort of the will to prevent it. Winking takes place involuntarily, whenever an object comes suddenly near or before the eyes, or when water needs to be carried off through the tear passage.]

Shakspeare calls this power "the mind's eye."

Hamlet." My father! Methinks I see my father.
Horatio.. -"Where, my Lord?

should wish to limit the application of the word conception to our sensations, and the objects of our perceptions. Dr. Reid, in his Inquiry, substitutes the word conception instead of the simple apprehension of the schools, and employs it in the same extensive signification. I think it may contribute to make our ideas more distinct, to restrict its meaning:- and for such a restriction, we have the authority of philosophers in a case perfectly analogous. In ordinary language, we apply the same word, perception, to the knowledge which we have by our senses of external objects, and to our knowledge of speculative truth: and yet an author would be justly censured, who should treat of these two operations of the mind under the same article of perception. I apprehend there is as wide a difference between the conception of a truth, and the conception of an absent object of sense, as between the perception of a tree, and the perception of a mathematical theorem. I have therefore taken the liberty to distinguish also the two former operations of the mind; and under the article of conception, shall confine myself to that faculty whose province it is to enable us to form a notion of our past sensations, or of the objects of sense that we have formerly perceived.*

man,

* [Stewart, who is a strict Nominalist, maintains that we can form a conception only of an individual object that can be perceived by the senses, -as of a particular house or tree. Reid and all other metaphysicians, except the Nominalists, maintain that we may have conceptions also of what abstract and general terms stand for; that is, they say we can apprehend the meaning of such words as wisdom, virtue, courage, etc., and also of triangle, man, tiger, — understanding thereby, not any particular triangle, or but the general idea answering to any or all triangles, any or all men, etc. If we did not apprehend their meaning, we could not argue about them, or use their names intelligibly. But the doctrine of the Nominalists is, that when we use these abstract, general terms, the mere words are our only objects of thought, and that we limit and fix the meaning of those words by calling up, when necessary, the image or conception of a particular thing comprehended under them. If I speak of a triangle in general, and wish to have something more definite before the mind than the mere word "triangle," they say that I call up the image of some particular triangle, and limit my attention, in considering it, to those qualities which it possesses in common with all triangles. According to the Nominalists,

Conception distinguished from Imagination. Conception is frequently used as synonymous with imagination. Dr. Reid says, that "imagination, in its proper sense, signifies a lively conception of objects of sight." "This is a talent," he remarks, "of importance to poets and orators; and deserves a proper name, on account of its connection with their arts." He adds, that "imagination is distinguished from conception as a part from the whole."

I shall not inquire at present into the proper English meaning of the words conception and imagination. In a study such as this, so far removed from common purposes of speech, some latitude may perhaps be allowed in the use of words; provided only we define accurately those we employ, and adhere to our own definitions.

The business of conception, according to the account I have given of it, is to present us with an exact transcript of what we have felt or perceived. But we have, moreover, a power of modifying our conceptions, by combining the parts of different ones together, so as to form new wholes of our own creation. I shall employ the word imagination to express this power; and, I apprehend, that this is the proper sense of the word, if imagination be the power which gives birth to the productions of the poet and the painter. This is not a simple faculty of the mind. It presupposes abstraction, to separate from each other qualities and circumstances which have been perceived in conjunction; and also judgment and taste, to direct us in forming the combinations. If they are made wholly at random, they are proofs of insanity.*

then, the only objects of thought are (1.) mere words, and (2.) the conceptions of particular, material objects, such as can be imaged or pictured forth in the fancy. Reid and the Conceptualists maintain, that there are also (3.) conceptions of abstract and general things, -conceptions which are more definite than mere words, but less definite than images or pictures of particular objects.

But these differences of opinion between the Nominalists, Realists, and Conceptualists, will be explained more fully hereafter.]

* In common discourse, we often use the phrase of thinking upon an object, to express what I here call the conception of it. In the following passage,