knowledge and a ready recollection of facts, and which, at the fame time, are yet in too imperfect a state to allow us to obtain just theories by the method of induction. This is particularly the cafe in the science of medicine, in which we are under a neceffity to apply our knowledge, fuch as it is, to practice. It is also, in fome degree, the cafe in agriculture. In the merely fpeculative parts of phyfics and chemistry, we may go on patiently accumulating facts, without forming any one conclufion, farther than our facts authorise us; and leave to posterity the credit of establishing the theory to which our labours are fubfervient. But in medicine, in which it is of confequence to have our knowledge at command, it feems reafonable to think, that hypothetical theories may be used with advantage; provided always, that they are confidered merely in the light of artificial memories, and that the student is prepared to lay them afide, or to correct them, in proportion as his knowledge of nature becomes more extenfive. I am, indeed, ready to confefs, that this is a caution which it is more eafy to give than to follow: for it is painful to change any of our habits of arrangement, and to relinquifh those fyftems in which we have been educated, and which have long flattered us with an idea of our own wif dom. Dr. Gregory mentions* it as a striking and diftinguishing circumftance in the character of Sydenham, that, although full of hypothetical reafoning, it did not render him the lefs attentive to obferva tion; and that his hypotheses seem to have fat fo

Lectures on the Duties and Qualifications of a Phyfician.

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loosely

loosely about him, that either they did not influence his practice at all, or he could eafily abandon them, whenever they would not bend to his experience.

SECTION V.

Continuation of the fame Subject.-Effects produced on the Memory by committing to Writing our acquired Knowledge.

H

AVING treated at confiderable length of the improvement of memory, it may not be improper, before leaving this part of the fubject, to confider what effects are likely to be produced on the mind by the practice of committing to writing our acquired knowledge. That fuch a practice is unfavourable, in some respects, to the faculty of memory, by fuper. feding, to a certain degree, the neceffity of its exertions, has been often remarked, and I believe is true; but the advantages with which it is attended in other respects, are so important, as to overbalance greatly this trifling inconvenience.

It is not my intention at prefent to examine and compare together the different methods which have been propofed, of keeping a common-place book. In this, as in other cafes of a fimilar kind, it may be difficult, perhaps, or impoffible, to establish any rules which will apply univerfally. Individuals must be left to judge for themselves, and to adapt their contrivances to the particular nature of their literary purfuits, and to their own peculiar habits of affociation and arrangement. The remarks which I am to offer

are

are very general, and are intended merely to illuftrate a few of the advantages which the art of writing affords to the philofopher, for recording, in the course of his progrefs through life, the results of his fpeculations, and the fruits of his experience.

The utility of writing, in enabling one generation to tranfmit its difcoveries to another, and in thus giv. ing rife to a gradual progress in the fpecies, has been fufficiently illuftrated by many authors. Little attention, however, has been paid to another of its effects, which is no lefs important; I mean, to the foundation which it lays for a perpetual progrefs in the intellectual powers of the individual.

It is to experience, and to our own reflections, that we are indebted for by far the most valuable part of our knowledge: and hence it is, that although in youth the imagination may be more vigorous, and the genius more original, than in advanced years; yet, in the case of a man of observation and inquiry, the judgment may be expected, at least as long as his faculties remain in perfection, to become every day founder and more enlightened. It is, however, only by the conftant practice of writing, that the refults of our experience, and the progress of our ideas, can be accurately recorded. If they are trufted merely to the memory, they will gradually vanish from it like a dream, or will come in time to be fo blended with the fuggeftions of imagination, that we fhall not be able to reafon from them with any degree of confidence. What improvements in fcience might we not flatter ourselves with the hopes of accomplishing, had we only activity and industry to treasure up every plaufible

plaufible hint that occurs to us! Hardly a day. paffes, when many fuch do not occur to ourselves, or are fuggefted by others: and detached and infulated, as they may appear at prefent, fome of them may perhaps afterwards, at the distance of years, furnish the key-stone of an important fyftem.

But it is not only in this point of view that the philofopher derives advantage from the practice of writing. Without its affiftance, he could feldom be able to advance beyond thofe fimple elementary truths which are current in the world, and which form, in the various branches of fcience, the established creed of the age he lives in. How inconfiderable would have been the progress of mathematicians, in their more abftrufe fpeculations, without the aid of the algebraical notation; and to what fublime discoveries have they been led by this beautiful contrivance, which, by relieving the memory of the effort neceffary for recollecting the fteps of a long investigation, has enabled them to profecute an infinite variety of inquiries, to which the unaffifted powers of the human mind would have been altogether unequal! In the other sciences, it is true, we have feldom or never occafion to follow out fuch long chains of confequences as in mathematics; but in thefe fciences, if the chain of inveftigation be fhorter, it is far more difficult to make the tranfition from one link to another; and it is only by dwelling long on our ideas, and rendering them perfectly familiar to us, that such tranfitions can, in most inftances, be made with fafety. In morals and politics, when we advance a step beyond those elementary truths which are daily prefented

G g

fented to us in books or converfation, there is no method of rendering our conclufions familiar to us, but by committing them to writing, and making them frequently the fubjects of our meditation. When we have once done fo, these conclufions become elementary truths with refpect to us; and we may advance from them with confidence to others which are more remote, and which are far beyond the reach of vulgar discovery. By fol lowing fuch a plan, we can hardly fail to have our industry rewarded in due time by fome important improvement; and it is only by fuch a plan that we can reasonably hope to extend confiderably the boundaries of human knowledge. I do not say that these habits of study are equally favourable to brilliancy of converfation. On the contrary, I believe that thofe men who poffefs this accomplishment in the highest degree, are fuch as do not advance beyond elementary truths; or rather, perhaps, who advance only a fingle step beyond them; that is, who think a little more deeply than the vulgar, but whofe conclufions are not fo far removed from common opinions, as to render it neceffary for them, when called upon to defend them, to exhaust the patience of their hearers, by ftating a long train of intermediate ideas. They who have pushed their inquiries much farther than the common systems of their times, and have rendered familiar to their own minds the intermediate steps by which they have been led to their conclufions, are too apt to conceive other men to be in the fame fituation with themselves; and when they mean to inftruct, are mortified to find that they are only regarded

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