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 consciousness, our conclufions will be no less certain, than those in phyfics: but if our curiofity leads us to attempt an explanation of the affociation of ideas, by certain fuppofed vibrations, or other changes, in the state 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 *.

The

* There is indeed one view of the connexion between Mind and Matter, which is perfectly agreeable to the juft rules of philofophy. 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 diftinct idea of this fort of fpeculation; and I do not know that much progrefs has yet been made in it. In his books de Augmentis Scientiarum, a variety of subjects are enumerated, in order to illuftrate its nature; and, undoubtedly, most of these are in a high degree curious and important. The following lift comprehends the chief of those he has mentioned; with the addition of feveral others, recommended to the confideration of Philofophers and of Medical Inquirers, by the late Dr. Gregory. See his Lectures on the Duties and Qualifications of a Phyfician.

1. The doctrine of the prefervation and improvement of the dif ferent fenfes.

2. The history of the power and influence of imagination. 3. The hiftory of the feveral species of enthufiafm.

4. The history of the various circumstances in parents, that have

an

The observations 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 these, 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 ftrange mixture of fact and hypothefis, which the greater part of metaphyfical inquiries exhibit, had led almost universally

an influence on conception, and the conftitution and characters of their children.

5. The history of dreams.

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

7. The history of the effects of mufic, and of such other things as operate on the mind and body, in confequence of impreffions

made on the fenfes.

8. The history of natural figns and language, comprehending the doctrine of phyfiognomy and of outward gesture.

9. The hiftory of the power and laws of the principle of imi

tation.

To this lift various other fubjects might be added; particularly, the history of the laws of memory, in fo far as they appear to be connected with the state of the body; and the history of the different fpecies of madness.

This view of the connexion between Mind and Matter does not fall properly under the plan of the following work; in which my leading object is to ascertain the principles of our nature, in for far as they can be discovered by attention to the subjects of our own consciousness; and to apply these principles to explain the phenomena arifing from them. Various incidental remarks, however, will occur in the course of our inquiries, tending to illustrate fome of the fubjects comprehended in the foregoing enumeration.

to

to a belief, that it is only a very faint and doubtful light, which human reason can ever expect to throw on this dark, but interesting, field of speculation.

Befide this inattention to the proper limits of philofophical inquiry, other fources of error, from which the science of physics is entirely exempted, have contributed to retard the progrefs of the philofophy of mind. Of these, the most important proceed from that disposition which is so natural to every person at the commencement of his philofophical pursuits, to explain intellectual and moral phenomena by the analogy of the material world.

1 before took notice of thofe habits of inattention to the fubjects of our consciousness, 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 consequence 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 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 circumstance, that we have scarcely any appropriated language with respect to mind, and that the words which express 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 pleased to fancy between them, can be of no use in illustrating either; and that it is no lefs unphilofo

phical 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 fuppofing, 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 obferved, 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 contraft between the metaphyfical fpeculations of fome of the most eminent philofophers in England at the end of the last 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 steps they had been used to, which, "by often treading, are worn into a smooth path." And Newton himself has propofed the following query, concerning the manner in which the mind perceives external objects. "Is not," (fays he,) "the fenforium of animals the place where the sen"tient fubftance is prefent, and to which the fen"fible fpecies of things are brought, through the

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nerves and brain, that they may be perceived by "the mind prefent in that place?"-In the course 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 spend fo much of their time in clearing away the rubbish collected by their predeceffors. This indeed was a preliminary step, which the ftate of the fcience, and the conclufions to which it had led, rendered abfolutely neceffary; for, however important the pofitive 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 philosophy, 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 propofed to himself in his metaphyfical inquiries; and to this object his labours have been directed with fo much ability, candour,

and