laft fuppofition would be perfectly analogous to Dr. Hartley's doctrine concerning the nature of our habitual exertions. The only plaufible objection which, I think, can be offered to the principles I have endeavoured to establish on this fubject, is founded on the aftonishing, and almost incredible rapidity, they neceffarily fuppofe in our intellectual operations.-When a perfon, for example, reads aloud; there muft, according to this doctrine, be a feparate volition preceding the articulation of every letter; and it has been found, by actual trial*, that it is poffible to pronounce about two thousand letters in a minute. Is it reasonable to fuppofe, that the mind is capable of fo many different acts in an interval of time fo very inconfiderable? With respect to this objection, it may be obferved, in the first place, that all arguments against the foregoing doctrine with refpect to our habitual exertions, in fo far as they are founded on the inconceivable rapidity which they fuppofe in our intellectual operations, apply equally to the common doctrine con. cerning our perception of difance by the eye. But this is not all. To what does the fuppofition amount, Incredibili velocitate peraguntur et repetuntur mufculorum contractiones. Docent curfus, præfertim quadrupedum, vel lingua, quæ quadringinta vocabula, forte bis mille literas, exprimit, fpatio temporis quod minutum vocare folemus, quamvis ad multas literas exprimendas plures mufculorum contractiones requirantur. Confpectus Medicine Theoretica, Aud. Jac. Gregory. which which is confidered as fo incredible? Only to this, that the mind is fo formed, as to be able to carry on certain intellectual proceffes, in intervals of time too fhort to be estimated by our faculties; a fuppofition which, fo far from being extravagant, is supported by the analogy of many of our most certain conclufions in natural philofophy. The discoveries made by the microscope, have laid open to our fenses a world of wonders, the existence of which hardly any man would have admitted upon inferior evidence; and have gradually prepared the way for thofe phyfical fpeculations, which explain fome of the most extraordinary phenomena of nature, by means of modifications of matter far too fubtile for the examination of our organs. Why then fhould it be confidered as unphilofophical, after having demonftrated the exiftence of various intellectual proceffes which escape our attention in confequence of their rapidity, to carry the fuppofition a little farther, in order to bring under the known laws of the human conftitution, a class of mental operations, which muft otherwife remain per- . fectly inexplicable? Surely, our ideas of time are merely relative, as well as our ideas of extenfion; nor is there any good reafon for doubting, that, if our powers of attention and memory were more perfect than they are, fo as to give us the fame advantage in examining rapid events, which the microscope gives for examining minute portions of extenfion, they would enlarge our views with refpect to the intellectual world, no less than that inftrument has with refpect to the material. It may contribute to remove, still more completely, fome of the fcruples which are naturally fuggefted by the foregoing doctrine, to remark, that, as the great ufe of attention and memory is to enable us to treasure up the refults 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 thofe intervals of time, which we have no occafion to estimate in the common business of life. All the intellectual proceffes I have mentioned are fubfervient to fome particular end, either of perception or of action; and it would have been perfectly fuperfluous, if, after this end were gained, the steps which are inftrumental in bringing it about, were all treafured up in the memory. Such a conftitution of our nature would have had no other effect but to store the mind with a variety of useless particulars. After all I have faid, it will perhaps be ftill thought, that some of the reasonings I have offered are too hypothetical; and it is even poffible, that fome may be disposed rather to difpute the common theory of vifion, than admit the conclufions I have endeavoured to establish. To such readers the following confiderations may be of ufe, as they afford a more palpable inftance, 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 obfervation of his eye, is conftantly requifite.-It is evident that the part of his body which fupports the object is never wholly at reft; otherwife the object would no more stand upon it, than if placed in the same. pofition upon a table. The equilibrift, therefore, muft watch, in the very beginning, every inclination of the object from the proper position, in order to counteract this inclination by a contrary movement. In this manner, the object has never time to fall in any one direction, and is fupported in a way fomewhat analogous to that in which a top is supported on a pivot, by being made to spin upon an axis.-That a perfon fhould be able to do this in the case of a single object, is curious; but that he fhould be able to balance in the fame way, two, or three, upon different parts of his body, and at the fame time balance himself on a small cord or wire, is indeed wonderful. Nor is it poffible to conceive that, in fuch an inftance, the mind, at one and the fame moment, attends to these different equilibriums; for it is not merely the attention which is requifite, but the eye. We must therefore conclude, that both of these are directed fucceffively to the different equilibriums, but change from one object to another with fuch velocity, that the effect, with refpect to the experiment, is the fame as if they were directed to all the objects conftantly. It is worth while to remark farther, with refpect to this last illuftration, that it affords direct evidence of the poffibility of our exerting acts of the will, which we are unable to recollect; for the movements of the equilibrift do not fucceed each other in a regular order, like thofe of the harpsichord player, in performing a piece of mufic; but muft in every inftance be regu lated lated by accidents, which may vary in numberless respects, and which indeed muft vary in numberless refpects, every time he repeats the experiment: and therefore, although, in the former cafe, we fhould fuppofe, with Hartley, "that the motions cling to "one another, and to the impreffions of the notes, "in the way of affociation, without any intervention "of the ftate of mind called will," yet, in this instance, even the poffibility of fuch a fuppofition is directly contradicted by the fact. The dexterity of jugglers (which, by the way, merits a greater degree of attention from philofophers, than it has yet attracted,) affords many curious illustrations of the fame doctrine. The whole of this art feems to me to be founded on this principle; that it is poffible for a perfon, by long practice, to acquire a power, not only of carrying on certain intellectual proceffes more quickly than other men, (for all the feats of legerdemain fuppofe the exercife of obfervation, 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 fhort to enable the fpectators to exert that degree of attention which is neceffary to lay a foundation for memory*. As fome philofophers have difputed the influence of the will in the cafe 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, (fay thefe philofophers,) that there are inftances in which we will an effect, without being able to make it an object of attention, * See Note [E]. |