I am not mistaken, been already decided by feveral philofophers in the negative; and I acknowledge, for my own part, that although their opinion has not only been called in question by others, but even treated with fome degree of contempt as altogether hypothetical, it appears to me to be the most reafonable and philofophical that we can form on the subject.

There is indeed a great variety of cafes, in which the mind apparently exerts different acts of attention at once; but from the inftances which have already been mentioned, of the aftonishing rapidity of thought, it is obvious, that all this may be explain. ed, without supposing these acts to be co-exiftent; and I may even venture to add, it may all be axplained in the most fatisfactory manner, without afcribing to our intellectual operations, a greater degree of rapidity than that with which we know from the fact that they are fometimes carried on. The effect of practice in increafing this capacity of apparently attending to different things at once, renders this explanation of the phenomenon in queftion, more probable than any other.

The cafe of the equilibrift and rope-dancer already mentioned, is particularly favourable to this explanation; as it affords direct evidence of the poffibility of the mind's exerting different fucceffive acts in an interval of time fo fhort, as to produce the fame fenfible effect, as if they had been exerted at one and the fame moment. In this cafe, indeed, the rapidity of thought is fo remarkable, that if the different acts of the mind were not all neceffarily accompanied with different movements of the eye, there can be no reafon for doubting, that the philofophers, whofe doctrine I am now controverting, would have asferted, that they are all mathematically co-exiftent.

Upon a queftion, however, of this fort, which does not admit of a perfectly direct appeal to the fact, I

would by no means be understood to decide with confidence; and therefore I fhould with the conclufions I am now to state, to be received as only conditionally established. They are neceffary and obvious confequences of the general principle," that the "mind can only attend to one thing at once;" but muft ftand or fall with the truth of that fuppofition..

It is commonly understood, I believe, that, in a concert of mufic, a good ear can attend to the dif ferent parts of the mufic separately, or can attend to them all at once, and feel the full effect of the harmony. If the doctrine, however, which I have endeavored to establish, be admitted, it will follow, that in the latter cafe, the mind is conftantly varying its attention from the one part of the mufic to the other, and that its operations are fo rapid, as to give us no perception of an interval of time.

The fame doctrine leads to fome curious conclu. fions with refpect to vifion. Suppofe the eye to be fixed in a particular pofition, 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 refult of the various perceptions we have of the different points in the outline? With refpect to this queftion, the principles already ftated lead me to conclude, that the mind does at one and the fame time perceive every point in the outline of the object, (provided the whole of it be painted on the retina at the fame inftant,) for perception, like consciousness, is an involuntary operation. As no two points, however, of the outline are in the fame direction, every point, by itself, conftitutes juft as diftinct an object of attention to the mind, as if it were separated by an interval of empty space from all the reft. If the doctrine therefore formerly stated be juft, it is impoffible for the mind to attend to more than one of these points at once; and as the perception of the figure of the object, im

plies a knowledge of the relative fituation of the different points with refpect to each other, we must conclude, that the perception of figure by the eye, is the refult of a number of different acts of attention. These acts of attention, however, are performed with fuch rapidity, that the effect, with refpect to us, is the fame as if the perception were inftantaneous.

In farther confirmation of this reafoning, it may be remarked, that if the perception of visible figure were an immediate confequence of the picture on the retina, we should have, at the first glance, as diftinct an idea of a figure of a thoufand fides, as of a triangle or a fquare. The truth is, that when the figure is very fimple, the process of the mind is fo rapid, that the perception feems to be inftantaneous; but when the fides are multiplied beyond a certain number, the interval of time neceffary 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 conftitutes this point one object of attention? The answer, I apprehend, is, that this point is the minimum vifibile. If the point be lefs, we cannot perceive it: if it be greater, it is not all feen 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.

CHAPTER THIRD.

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 exclufively the proper meaning of the word, but I think that the faculty which I have now defined deferves to be diftinguished by an appropriated name.

ers.

Conception is often confounded with other pow

When a painter makes a picture of a friend, who is abfent or dead, he is commonly faid to paint from memory: and the expreffion is fufficiently correct for common converfation. But in an analyfis of the mind, there is ground for a diftinction. The power of conception enables him to make the features of his friend an object of thought, fo as to copy the resemblance; the power of memory recognifes 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 correfponds to what was called by the schoolmen fimple apprehenfion; with this difference only, that they included, under this name, our apprehenfion of general propofitions; whereas I fhould wish to limit the application of the word conception to our fenfations, and the objects of our perceptions. Dr. Reid, in his Inquiry, fubftitutes the word con

* Shakespeare calls this power "the mind's eye."
Hamlet." My father! Methinks I see my father.
Horatio." Where, my Lord?

Hamlet." In my mind's eye, Horatio."

Act i. Scene 4.

Q

ception instead of the fimple apprehenfion of the schools, and employs it in the fame extenfive fignificacation. I think it may contribute to make our ideas more diftinct, to reftrict its meaning :-and for fuch a restriction, we have the authority of philofophers in a cafe perfectly analogous.-In ordinary language, we apply the fame word perception, to the knowledge which we have by our fenfes of external objects, and to our knowledge of fpeculative truth: and yet an author would be justly cenfured, who should treat of these two operations of the mind under the fame 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 fenfe, as between the perception of a tree, and the perception of a mathematical theorem.-I have therefore taken the liberty to distinguish alfo the two former operations of the mind and under the article of conception fhall confine myself to that faculty whofe province it is to enable us to form a notion of our past fenfations, or of the objects of sense that we have formerly perceived.

Conception is frequently used as fynonymous with imagination. Dr. Reid fays, that "imagination, in "its proper fenfe, fignifies a lively conception of objects of fight." This is a talent" (he remarks) "of importance to poets and orators; and deferves 66 a proper name, on account of its connexion with "their arts." He adds, that "imagination is dif "tinguished from conception, as a part from a "whole."

I fhall not inquire, at prefent, into the proper English meaning of the words conception and imagination. In a ftudy fuch as this, fo far removed from the common purposes of speech, fome latitude may perhaps be allowed in the ufe of words; provided only we define accurately thofe we employ, and adhere to our own definitions.