pect clears up; and the phenomena, which appeared, at first, to be too various for our comprehenfion, are found to be the refult of a comparatively small number of fimple and uncompounded faculties, or of fimple and uncompounded principles of action. Thefe faculties and principles are the general laws of our conftitution, and hold the fame place in the philofophy of mind, that the general laws we inveftigate in phyfics, hold in that branch of fcience. In both cafes, the laws which nature has eftablished, are to be investigated only by an examination of facts; and in both cafes, a knowledge of these laws leads to an explanation of an infinite number of phenomena.

In the investigation of phyfical laws, it is well known, that our inquiries must always terminate in fome general fact, of which no account can be given, but that fuch is the conftitution of nature. After we have eftablished, for example, from the aftronomical phenomena, the univerfality of the law of gravitation, it may ftill be asked, whether this law implies the conftant agency of mind; and (upon the fuppofition that it does) whether it be probable that the Deity always operates immediately, or by means of fubordinate inftruments? But thefe queftions, however curious, do not fall under the province of the natural philofopher. It is fufficient for his pofe, if the univerfality of the fact be admitted.

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The cafe is exactly the fame in the philofophy of mind. When we have once afcertained a general fact; fuch as, the various laws which regulate the affociation of ideas, or the dependence of memory on that effort of the mind which we call Attention; it is all we ought to aim at, in this branch of science. If we proceed no farther than facts for which we have the evidence of our own confcioufnefs, our conclufions will be no lefs certain, than thofe in phyfics: but if our curiofity leads us to atC

tempt an explanation of the affociation of ideas, by certain fuppofed vibrations, or other changes, in the ftate of the brain; or to explain memory, by means of fuppofed impreffions and traces in the fenforium; we evidently blend a collection of important and well afcertained truths, with principles which reft wholly on conjecture.*

*There is indeed one view of the connexion between Mind and Matter, which is perfectly agreeable to the just rules of philosophy. The object of this is, to ascertain the laws which regulate their union, without attempting to explain in what manner they are united.

Lord Bacon was, I believe, the first who gave a distinct idea of this sort of speculation; and I do not know that much progress has yet been made in it. In his books de Augmentis Scientiarum, & variety of subjects are enumerated, in order to illustrate its nature; and, undoubtedly, most of these are in a high degree curious and important. The following list comprehends the chief of those he has mentioned; with the addition of several others, recommended to the consideration of Philosophers and of Medical Inquirers, by the late Dr. Gregory. See his Lectures on the Duties and Qualifica tions of a Physician.

1. The doctrine of the preservation and improvement of the dif ferent senses.

2. The history of the power and influence of imagination. 3. The history of the several species of enthusiasm.

4. The history of the various circumstances in parents, that have an influence on conception, and the constitution and characters of their children.

5. The history of dreams.

6. The history of the laws of custom and habit.

7. The history of the effects of music, and of such other things as operate on the mind and body, in consequence of impressions made on the senses.

8. The history of natural signs and language, comprehending the doctrine of physiognomy and of outward gesture.

9. The history of the power and laws of the principle of imita tion.

To this list various other subjects might be added; particularly, the history of the laws of memory, in so far as they appear to be connected with the state of the body; and the history of the dif ferent species of madness.

This view of the connection between Mind and Matter does not fall properly under the plan of the following work; in which my

The obfervations which have been now stated, with refpect to the proper limits of philofophical curiofity, have too frequently escaped the attention of speculative men, in all the different departments of science. In none of thefe, however, has this inattention produced fuch a variety of errors and abfurdities, as in the science of mind; a fubject to which, till of late, it does not seem to have been fufpected, that the general rules of philofophifing are applicable. The strange mixture of fact and hypothefis, which the greater part of metaphyfical inquiries exhibit, had led almost universally to a belief, that it is only a very faint and doubtful light, which human reafon can ever expect to throw on this dark, but interesting, field of fpeculation.

Befide this inattention to the proper limits of philofophical inquiry, other fources of error, from which the fcience of phyfics is entirely exempted, have contributed to retard the progrefs of the philofophy of mind. Of thefe, the most important proceed from that difpofition which is fo natural to every perfon at the commencement of his philofophical pursuits, to explain intellectual and moral phenomena by the analogy of the material world.

I before took notice of those habits of inattention to the fubjects of our confcioufnefs, which take their rife in that period of our lives when we are neceffarily employed in acquiring a knowledge of the properties and laws of matter. In confequence of this early familiarity with the phenomena of the material world, they appear to us lefs myfterious than those of mind; and we are apt to think that

leading object is to ascertain the principles of our nature, in so far as they can be discovered by attention to the subjects of our own consciousness; and to apply these principles to explain the phenomena arising from them. Various incidental remarks, however, will occur in the course of our inquiries, tending to illustrate some of the subjects comprehended in the foregoing enumeration.

we have advanced one step in explaining the latter, when we can point out fome analogy between them and the former. It is owing to the fame circumftance, that we have scarcely any appropriated language with refpect to mind, and that the words which exprefs its different operations, are almost all borrowed from the objects of our fenfes. It muft, however, appear manifeft, upon a very little reflection, that as the two fubjects are effentially diftinct, and as each of them has its peculiar laws, the analogies we are pleafed to fancy between them, can be of no ufe in illuftrating either; and that it is no lefs unphilofophical to attempt an explanation of perception, or of the affociation of ideas, upon mechanical principles; than it would be to explain the phenomena of gravitation, by supposing, as fome of the ancients did, the particles of matter to be animated with principles of motion; or to explain the chemical phenomena of elective attractions, by fuppofing the fubftances among which they are observed, to be endowed with thought and volition.-The analogy of matter, therefore, can be of no use in the inquiries which form the object of the following work; but, on the contrary, is to be guarded against, as one of the principal fources of the errors to which we are liable.

Among the different philofophers who have fpeculated concerning the human mind, very few indeed can be mentioned, who have at all times been able to guard against analogical theories. At the fame time, it must be acknowledged, that fince the publication of Des Cartes' writings, there has been a gradual, and, on the whole, a very remarkable improvement in this branch of science. One ftriking proof of this is, the contrast between the metaphyfical fpeculations of fome of the moft eminint philofophers in England at the end of the laft century, and those which we find in the fyftems, however imperfect, of

the prefent age. Would any writer now offer to the world, fuch conclufions with refpect to the mind, as are contained in the two following paffages from Locke and Newton? "Habits," (fays Locke,) "feem "to be but trains of motion, in the animal fpirits, "which, once fet a-going, continue in the fame fteps "they had been ufed to, which, by often treading, "are worn into a smooth path." And Newton himfelf has propofed the following query, concerning the manner in which the mind perceives external objects. "Is not," (fays he,)" the fenforium of animals the <c place where the fentient fubftance is prefent, and "to which the fenfible species of things are brought, "through the nerves and brain, that they may be "perceived by the mind prefent in that place?"In the courfe of the following Effays, I fhall have occafion to quote various other paffages from later writers, in which an attempt is made to explain the other phenomena of mind upon fimilar principles.

It is however much to be regretted, that even fince the period when philofophers began to adopt a more rational plan of inquiry with refpect to fuch fubjects, they have been obliged to fpend fo much of their time in clearing away the rubbish collected by their predeceffors. This indeed was a preliminary ftep, which the state of the science, and the conciufions to which it had led, rendered abfolutely neceffary; for, however important the positive advantages may be, which are to be expected from its future progrefs, they are by no means fo effential to human improvement and happiness, as a fatisfactory refutation of that fceptical philofophy, which had ftruck at the root of all knowledge, and all belief. Such a refutation feems to have been the principal object which Dr. Reid proposed to himself in his metaphysical inquiries; and to this object his labours have been directed with fo much ability, candor, and perfeverance, that unless future fceptics fhould occupy