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fact; such as, the various laws which regulate the association 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 conclusions will be no less certain, than those in physics : but if our curiosity leads us to attempt 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 supposed impressions and traces in the sensorium ; we evidently blend a collection of important and well-ascertained truths, with principles which rest wholly on conjecture *.

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* There is indeed one view of the connexion between Mind and Matter, which is perfectly agreeable to the just 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 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 confideration of Philosophers 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 preservation and improvement of the dif. ferent fenfes.

2. The history of the power and influence of imagination. 3. The history of the several species of enthufiafm. 4. The history of the various circumstances in parents, that have

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The observations which have been now stated, with respect to the proper limits of philosophical 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 philosophising are applicable. The strange mixture of fact and hypothesis, which the greater part of metaphysical inquiries exhibit, had led almost universally

an infuence 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 figns and language, comprehending the doctrine of phyfiognomy and of outward gesture.

9. The history of the power and laws of the principle of imi. tation.

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 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 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, how- . ever, will occur in the course of our inquiries, tending to illustrate some of the subjects comprehended in the foregoing enumeration.

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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.

Beside this inattention to the proper limits of philosophical 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 so 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 some analogy between them and the former. It is owing to the same 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 senses. It must, however, appear manifest, upon a very little reflection, that as the two subjects are essentially distinct, 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 less unphilosophical to attempt 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 some 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 supposing the substances among which they are observed, to be endowed with thought and volition. The analogy of matter, therefore, can be of no use in the in. quiries which form the object of the following work ; but, on the contrary, is to be guarded against, as one of the principal sources of the errors to which we are liable.

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 publication of Des Cartes' writings, there has been a

gradual, and, on the whole, a very remarkable im. i provement in this branch of science. One striking

proof of this is, the contrast between the metaphyfical speculations of some of the most eminent philosophers in England at the end of the last century, and those which we find in the systems, however imperfect, of 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 ? (says Locke,) “ seem to be but trains of motion, in “ the animal spirits, which, once set a-going, continue

“ Habits,

« in the same steps they had been used to, which, “ by often treading, are worn into a smooth path.” And Newton himself has proposed the following query, concerning the manner in which the mind perceives external objects. “ Is not,” (says he,) “ the sensorium of animals the place where the sen“ tient substance is present, and to which the fen“ fible 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 following Essays, I shall have occasion to quote various other passages 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 predecessors. This indeed was a preliminary step, which the state of the science, and the conclusions to which it had led, rendered absolutely neceffary; for, however important the positive advantages may be, which are to be expected from its future progress, they are by no means so essential to human improvement and happiness, as a satisfactory refutation of that sceptical philosophy, which had struck at the root of all knowledge, and all belief. Such a refutation seems 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 ability, candour,

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