account can be given, but that such is the constitution of nature. After we have established, for example, from the astronomical phenomena, the universality of the law of gravitation, it may still be asked, whether this law implies the constant agency of mind; and (upon the supposition that it does) whether it be probable that the Deity always operates immediately, or by means of subordinate instruments? But these questions, however curious, do not fall under the province of the natural philosopher. It is sufficient for his purpose, if the universality of the fact be admitted.

The case is exactly the same in the philosophy of mind. When we have once ascertained a general 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.*

* 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 late 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 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, however, will occur in the course of our inquiries, tending to illustrate some of the subjects comprehended in the foregoing enumeration.

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 philosophizing are applica ble. 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.

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 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 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 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 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 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 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 labors have been directed with so much ability, candor, and perseverance, that unless future skeptics 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 foundations laid, it is time to begin the super

This theory, with respect to Habits, is very closely copied from Malebranche. "Il faut remarquer que les esprits ne trouvent pas toujours les chemins, par où ils doivent passer, assez ouverts et assez libres ; et que cela fait, que nous avons de la difficulté à remuer, par exemple, les doigts avec la vitesse qui est nécessaire pour jouer des instrumens de musique, ou les muscles qui servent à la prononciation, pour prononcer les mots d'une langue étrangère; mais que peu à peu les esprits animaux, par leur cours continuel, ouvrent et applanissent ces chemins, ensorte qu' avec le tems, ils ne trouvent plus de resistance. Car c'est dans la facilité que les esprits animaux ont de passer dans les membres de nôtre corps, que consistent les habitudes."—Rech. de la Vérité, Liv. ii. chap. 5.

structure. 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 consider ation of those questions which have been agitated in the present age, between the patrons of the skeptical 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 skeptical 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 endeavor to explain, at some length, in the following section.

PART II.

SECTION I.

Of the Utility of the Philosophy of the Human Mind.

IT has been often remarked, that there is a mutual connexion 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 confined his studies wholly to one branch of knowledge. That curiosity, which he has been accustomed to indulge in the course of his favorite pursuit, will naturally extend itself to every remarkable object which falls under his observation, and can scarcely fail to be a source of perpetual dissatisfaction to his mind, till it has been so far gratified as to enable him to explain all the various phenomena which his professional habits are every day presenting to his view.

As every particular science is in this manner connected with others, to which it naturally directs the attention, so all the pursuits of life, whether they terminate in speculation or action, are connected with that general science which has the human mind for its object. The powers of the understanding are instruments which all men employ; and his curiosity must be small indeed, who passes through life in total ignorance of faculties which his wants and necessities force him habitually to exercise, and which so remarkably distinguish man from the lower animals. The active principles of our nature, which, by their various modifications and combinations, give rise to all the moral differences among men, are fitted, in a still higher degree, if possible, to interest those who are either disposed to reflect on their own characters, or to observe, with attention, the characters of others. The phenomena resulting from these faculties and principles of the mind, are every moment soliciting our notice, and open to our examination a field of discovery, as inexhaustible as the phenomena of the material world, and exhibiting not less striking marks of divine wisdom.

While all the sciences and all the pursuits of life have this common tendency to lead our inquiries to the philosophy of human nature, this last branch of knowledge borrows its principles from no other science whatever. Hence there is something in the study of it which is peculiarly gratifying to a reflecting and inquisitive mind, and something in the conclusions to which it leads on which the mind rests with peculiar satisfaction. Till once our opinions are in some degree fixed with respect to it, we abandon ourselves, with reluctance, to particular scientific investigations; and, on the other hand, a general knowledge of such of its principles as are most fitted to excite the curiosity, not only prepares us for engaging in other pursuits with more liberal and comprehensive views, but leaves us at liberty to prosecute them with a more undivided and concentrated attention.

It is not, however, merely a subject of speculative curiosity that the principles of the human mind deserve a careful examination. The advantages to be expected from a successful analysis of