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these, however, has this inattention produced such a variety of errours 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 philosophizing 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 interesting, field of speculation. Besides this inattention to the proper limits of philosophical inquiry, other sources of errour, 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 dis^, tinct, and as each of them has its peculiar laws, the analo
gies we are pleased to fancy between them, can be of he 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 inquiries 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 errours 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 improvement in this branch of science. One striking proof of this is, the contrast between the metaphysical 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 : “Habits,” (says Locke,) “seem to be but trains of motion, “in the animal spirits, which, once set a-going, continue “in the same steps they had been used to, which, by of. “ten 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 sentient substance is present, and to which “the sensible 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 necessary; 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 Jonowledge 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, and perseverance, that unless future sceptics should occupy a ground very different from that of their predecessors, it is not likely that the controversy will ever be renewed. The rubbish being now removed, and the fourdations laid, it is time to begin the superstructure. The - progress which I have made in it is, I am sensible, very inconsiderable ; yet I flatter myself, that the little I have done, will be sufficient to illustrate the importance of the study, and to recommend the subjects, of which I am to treat, to the attention 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 connection 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 philosophy.
To what purposes the philosophy of the human mind, according to the view which I propose to take of it, is subservient, I shall endeavour to explain, at some length, in the following section.
Of the Utility of the Philosophy of the Human Mind.
It has been often remarked, that there is a mutual connection between the different arts and sciences; and that the improvements which are made in one branch of human knowledge, frequently throw light on others, to which it has apparently a very remote relation. The modern discoveries in astronomy, and in pure mathematics, have contributed to bring the art of navigation to a degree of perfection formerly unknown. The rapid progress which has been lately made in astronomy, anatomy, and botany, has been chiefly owing to the aid which these sciences have received from the art of the optician. Although, however, the different departments of science and of art mutually reflect light on each other, it is not always necessary either for the philosopher or the artist to aim at the acquisition of general knowledge. Both of them may safely take many principles for granted, without being able to demonstrate their truth. A seaman, though ignorant of mathematics, may apply, with correctness and dexterity, the rules for finding the longitude : An astronomer, or a botanist, though ignorant of optics, may avail himself of the use of the telescope, or the microscope. These observations are daily exemplified in the case of the artist; who has seldom either inclination or leisure to speculate concerning the principles of his art. It is rarely, however, we meet with a man of science, who has confin