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last supposition would be perfectly analogous to Dr. Hartley's doctrine concerning the nature of our habitual exertions.

The only plausible objection which, I think, can be offered to the principles I have endeavoured to establish on this subject, is founded on the astonishing, and almost incredible rapidity, they necessarily suppose in our intellectual operations.—When a person, for example, reads aloud ; there must, according to this doctrine, be a separate volition preceding the articulation of every letter ; and it has been found, by actual trial*, that it is possible to pronounce about two thousand letters in a minute. Is it reasonable to suppose, that the mind is capable of so many different acts in an interval of time so

very

inconsiderable ?

With respect to this objection, it may be observedon in the first place, that all arguments against the foregoing doctrine with respect to our habitual exertions, in so far as they are founded on the inconceivable rapidity which they suppose in our intellectual operations, apply equally to the common do&trine con. cerning our perception of disance by the eye. But this is not all. To what does the supposition amount, which is considered as so incredible ? Only to this, that the mind is so formed, as to be able to carry on certain intellectual processes, in intervals of time too short to be estimated by our faculties ; a supposition which, so far from being extravagant, is supported by the analogy of many of our most certain conclusions in natural philosophy. The discoveries made by the microscope, have laid open to our senses a world of wonders, the existence of which hardly any man would have admitted upon inferior evidence ; and have gradually prepared the way for those physical speculations, which explain some of the most extraordinary phenomena of nature, by means of modifications of matter far too subtile for the examination of our organs. Why then should it be considered as unphilosophical, after having demonstrated the existence of various intellectual processes which escape our attention in consequence of their rapidity, to carry the supposition a little farther, in order to bring under the known laws of the human constitution, a class of mental operations, which must otherwise remain per- . fectly inexplicable? Surely, our ideas of time are merely relative, as well as our ideas of extenfion; nor is there any good reason for doubting, that, if our powers of attention and memory were more perfect than they are, so as to give us the same advantage in cxamining rapid events, which the microscope gives for examining minute portions of extension, they would enlarge our views with respect to the intellectual world, no less than that instrument has with respect to the material.

* Incredibili velocitate peraguntur et repetuntur musculorum contractiones. Docent cursus, præfertim quadrupedum; vel lingua, quæ quadringinta vocabula, forte bis mille literas, exprimit, fpatio temporis quod minutum vocare folemus, quamvis ad multas liicras exprimendas plures musculorum contra&tiones requirantur. Confpetus Medicine Theoretica, Aut. Jac. Gregory.

Edit. altera, p. 171.
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contribute to remove, still more completely, some of the scruples which are naturally suggested by the foregoing doctrine, to remark, that, as the great use of attention and memory is to enable us to treasure up the results of our experience and reflexion for the future regulation of our conduct, it would have anfwered no purpose for the author of our nature to have extended their province to those intervals of time, which we have no occasion to estimate in the common business of life. All the intellectual processes I have mentioned are subservient to some particular end, either of perception or of action; and it would have been perfectly superfluous, if, after this end were gained, the steps which are instrumental in bringing it about, were all treasured up in the memory. Such a constitution of our nature would have had no other effect but to store the mind with a variety of useless particulars.

After all I have said, it will perhaps be still thought, that some of the reasonings I have offered are too hypothetical ; and it is even possible, that some may be disposed rather to dispute the common theory of vision, than admit the conclusions I have endeavoured to establish. To such readers the following considerations may be of use, as they afford a more palpable instance, than any I have yet mentioned, of the rapidity with which the thoughts may be trained by practice, to shift from one thing to another.

When an equilibrist balances a rod upon his finger, not only the attention of his mind, but the observation of his eye, is constantly requisite. It is evident that the part of his body which supports the object is

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never wholly at rest; otherwise the object would no more stand upon it, than if placed in the same position upon a table. The equilibrist, therefore, inust watch, in the very beginning, every inclination of the object from the proper position, in order to counteract this inclination by a trary movement. In this manner, the object has never time to fall in any one direction, and is supported in a way somewhat analogous to that in which a top is supported on a pivot, by being made to spin upon an axis.—That a person should be able to do this in the case of a single object, is curious; but that he should be able to balance in the same way, two, or three, upon different parts of his body, and at the same time balance himself on a small cord or wire, is indeed wonderful. Nor is it possible to conceive that, in such an instance, the mind, at one and the same moment, attends to these different equilibriums; for it is not merely the attention which is requisite, but the eye. We must therefore conclude, that both of these are directed successively to the different equilibriums, but change from one object to another with such velocity, that the effect, with respect to the experiment, is the same as if they were directed to all the objects constantly.

It is worth while to remark farther, with respect to this last illustration, that it affords direct evidence of the possibility of our exerting acts of the will, which we are unable to recollect; for the movements of the equilibrist do not succeed each other in a regular order, like those of the harpsichord player, in performing a piece of music; but must in every instance be regu. lated by accidents, which may vary in numberless re. spects, and which indeed must vary in numberless respects, every time he repeats the experiment: and therefore, although, in the former case, we should fuppose, with Hartley, “ that the motions cling to “ one another, and to the impressions of the notes, “ in the way of association, without any intervention " of the state of mind called will,” yet, in this instance, even the possibility of such a supposition is directly contradicted by the fact.

lated

The dexterity of jugglers (which, by the way, merits a greater degree of attention from philosophers, than it has yet attracted,) affords many curious illus, trations of the same doctrine. The whole of this art feems to me to be founded on this principle; that it is possible for a person, by long practice, to acquire a power, not only of carrying on certain intellectual processes more quickly than other men, (for all the feats of legerdemain suppose the exercise of observation, thought, and volition,) but of performing a variety of movements with the hand, before the eyes of a company, in an interval of time too short to enable the spectators to exert that degree of attention which is necessary to lay a foundation for memory

As some philosophers have disputed the influence of the will in the case of habits, fo others (particularly Stahl and his followers) have gone into the oppofite extreme, by referring to the will all the vital motions. If it be admitted, (say these philosophers,) that there are instances in which we will an effect, without being able to make it an object of attention, • See Note [E].

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