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tempt an explanation of the association of ideas, by certain supposed vibrations, or other changes, in the state of the brain; or to explain memory, by means of fuppofed impressions and traces in the sensorium ; we evidently blend a collection of important and well ascertained truths, with principles which rest 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, a 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 Jate Dr. Gregory. See his Lectures on the Duties and Qualifications of a Physician.

1. The doctrine of the preservation and improvement of the different 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 imitation.

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 different 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 observations which have been now stated, with respect to the proper limits of philofophical curiosity, 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 such a variety of errors and absurdities, as in the science of mind; a subject to which, till of late, it does not seem to have been suspected, that the general rules of philofophising are applicable. The strange mixture of fact and hypothesis, which the greater part of metaphysical inquiries exhibit, had led almost universally 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 intereft. ing, field of speculation.

Belide this inattention to the proper limits of philofophical inquiry, other sources of error, from which the science of physics is entirely exempted, have contributed to retard the progress of the philosophy of mind. Of these, the most important proceed from that disposition which is fo natural to every person at the commencement of his philosophical 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 subjects of our consciousness, which take their rise in that period of our lives when we are necessarily 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 less mysterious 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 hetween them and the former. It is owing to the fame circumftance, 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 senses. It must, however, appear manifest, upon a very little reflection, that as the two subjects are effentially distinct, and as each of them has its peculiar laws, the analo. gies we are pleased to fancy between them, can be of no use in illustrating either; and that it is no less unphilosophical to atteinpt an explanation of perception, or of the association 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 maiter to be animated with principles of motion; or to explain the chemical phenomena of elective attractions, by fuppfing 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,

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.

Among the different philosophers who have speculated concerning the human mind, very few indeed can be mentioned, who have at all times been able to guard against analogical theories. At the same time, it must be acknowledged, that since the publi. cation of Des Cartes' writings, there has been a gradual, and, on the whole, a very remarkable improvement in this branch of science. One striking proof of this is, the contrast between the metaphysical speculations of fome of the most eminint philosophers in England at the end of the last century, and those which we find in the fyftenis, however imperfect, of

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the present age. Would any writer now offer to the world, such conclusions with respect to the mind, as are contained in the two following passages from Locke and Newton ? “Habits,” (says Locke,)“ seem

to be but tra ns of motion, in the animal spirits, which, once set a-going, continue in the fame steps they had been used to, which, hy often treading,

are worn into a smooth path.”. And Newtor hiinself has proposed the folloing query, concerning the manner in which the mind perceives externalobjects. “ Is not,” (says he,)“ the sensorium of animals the.

place where the sentient substance is present, and - to which the fenfible species of things are brought, " through the nerves and brain, that they may be

perceived by the mind present in that place?". In the course of the foliowing Efsays, I shall have occafion to quote various other piffages from later writers, in which an attempt is made to explain the other phenomena of mind upon similar principles.

It is however much to be regretted, that even since the period when philosophers began to adopt a more rational plan of inquiry with respect to such subjects, they have been obliged to spend so much of their time in clearing away the rubbish collected by their predeceffors. This indeed was a preliminary step, which the state of the science, and the conciu. fions to which it had led, rendered absolutely necessary; for, however important the positive advantages may be, which are to be expected fronı its future progress, they are by no means fo essential to human improvement and happiness, as a fatisfactory refuta. tion of that sceptical philofophy, which had ftruck at the root of all knowledge, and ail 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 so much a ility, candor, and perseverance, that unless future sceptics should occupy a ground very different from that of their predecesfors, it is not likely that the controversy will ever be renewed. The rubbish being now removed, and the foundations laid, it is time to begin the superstructure. The progress which I have made in it is, I am fenfible, very inconsiderable ; yet I flatter myself, that the little I have done, will be sufficient to il. lustrate the importance of the study, and to recommend the subjects of which I am to treat, to the altention of others.

After the remarks which I have now made, the reader will not be surprised to find, that I have studiously avoided the consideration of those questions which have been agitated in the present age, between the patrons of the sceptical philosophy, and their opponents. These controversies have, in truth, no peculiar connexion with the inquiries on which I am to enter. It is indeed only by an examination of the principles of our nature, that they can be brought to a satisfactory conclusion ; but supposing them to remain undecided, our sceptical doubts concerning the certainty of human knowledge, would no more affect the philosophy of mind, than they would affect any of the branches of physics; nor would our doubts concerning even the existence of mind, affect this branch of science, any more than the doubts of the Berkeleian, concerning the existence of matter, affect his opinions in natural philofophy.

To what purposes the philosophy of the human mind according to the view which I propose to take of it, is subfervient, I shall endeavor to explain, at fome length, in the following section.

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