Lectures on the Philosophy of the Human Mind (Vol. 1 of 3)

On these general laws of inquiry, as relating alike to the investigation of the properties of matter and of mind, it is my intention to dwell, for some time, with full discussion; for, though the subject may be less pleasing, and may require more severe and unremitting attention on your part, than the greater number of the inquiries which await us, it is still more important than any of these, because it is, in truth, essential to them all. The season of your life is not that which gathers the harvest; it is that which prepares the soil, by diligent cultivation, for the fruits which are to adorn and enrich it; – or, to speak without a metaphor, you do not come here, that you may make yourselves acquainted, in a few months, with all the phenomena of the universe, – as if it were only to look on the motions of the planets in an orrery, or to learn a few names of substances and qualities, – but that you may acquire those philosophical principles, which in the course of a long and honourable life, are to enable you to render yourselves more familiar every day with the works of nature, and with the sublime plans of its beneficent Author: – and if without the knowledge of a single word of fact, in matter or in mind, it were possible for you to carry away from these walls a clear notion of the objects of inquiry, and of the plan on which alone investigation can be pursued with advantage, I should conceive, that you had profited far more, than if, with confused notions of the objects and plan of investigation, you carried with you the power of talking fluently, of observations, and experiments, and hypotheses, and systems, and of using, in their proper places, all the hardest words of science.

I must remark, however, that I should not have thought it necessary, thus to direct so much of your attention to the principles of scientific inquiry in general, if I could have taken for granted, that you had already enjoyed the benefit of the instruction of my illustrious colleague in another Chair, whose Lectures on Natural Philosophy, exemplifying that soundness of inquiry, which I can only recommend, would, in that case, have enlightened you more, as to the principles of physical investigation, than any mere rules, of which it is possible to point out to you the utility and the excellence.

All physical science, whatever may be the variety of objects, mental or material, to which it is directed, is nothing more than the comparison of phenomena, and the discovery of their agreement or disagreement, or order of succession. It is on observation, therefore, or on consciousness, which is only another name for internal observation, that the whole of science is founded; because there can be no comparison, without observation of the phenomena compared, and no discovery of agreement or disagreement, without comparison. So far, then, as man has observed the phenomena of matter or of mind, so far, and no farther, may he infer, with confidence, the properties of matter and of mind; or, in the words of the great primary aphorism of Lord Bacon, which has been so often quoted, and so often quoted in vain, “Homo, naturæ minister et interpres, tantum facit et intelligit, quantum de naturæ ordine re vel mente observaverit; nec amplius scit aut potest.”21

What is it that we truly mean, however, when we say, that we are about to inquire into the nature and properties of any substance? The question is a most important one, and is far from being so simple as it may at first appear. From the mere misunderstanding of the import of this question, the brightest talents of a long succession of ages, – talents, which, with clearer views of this single point, might have anticipated all the discoveries of our own time, and introduced us, perhaps, to discoveries still more brilliant and astonishing, were wasted in inquiries as barren as the frivolous glory which attended them, – that produced indeed much contention, and more pride, but produced nothing more; and, without giving any additional knowledge, took away from ignorance only its humility, and its power of being instructed.

What is it that we truly have in view, or should have in view, when we inquire into the nature of a substance?

The material universe, and all the separate substances which compose it, may be considered in two lights, – either simply, as composed of parts that co-exist, and are to our feelings continuous, so as to form, of many separate and independent elements, one apparent whole; or of parts that change their relative positions, constituting, by this change of place, all the physical events of the material system of the world; and inquiry may have reference to a substance in both, or either of those points of view. What is this body? may be inquired of us, when any particular body is pointed out; and the answer which we give will be very different according to the particular light in which we may have viewed it, though it must always relate to it in one or other of these two aspects. Let us suppose, for example, the body, concerning which the question is put, to be a piece of glass; I select intentionally a substance which is familiar to you all, and of which many of you probably have sufficient chemical knowledge to be acquainted with the composition. It may be asked of us, then, What is the substance termed glass? and our answer will vary, as I have said, with the view which we take of it. If we consider it merely as a continuous whole, our answer will be, that it is a compound of alkaline and siliceous matter– meaning that particles of alkali and flint co-exist, and are apparently continuous, in that mass of which we speak.

Such is one of the answers which may be given to the question; and this sort of answer is one which is very commonly given to such questions. It is, you will perceive, nothing more than the enumeration of the constituent parts of the substance, and considers the substance, simply as it exists alone, without regard to any other bodies that may exist around it, or near it, and without any allusion to change of any kind.

This sort of view, however, may be altogether reversed; and, instead of thinking of the parts that exist together in the substance, without reference to any changes, of which it is either the agent or the subject, we may think only of such changes, without reference to its constituent parts.

In this latter point of view, we may say, in answer to the question, as to the nature of the substance termed glass, that it is a transparent substance, which, according to the general laws of refraction, bends the light that passes through it variously, according to the different density of the medium through which the rays have immediately passed before arriving at it, or of the medium, through which they are to pass after penetrating it; that it is a substance fusible at a certain temperature, not dissolved by the common powerful acids, but soluble in a particular acid termed the fluoric acid; that, when strongly rubbed, by certain other substances, it communicates, for a time, to various bodies, the power of attracting or repelling other bodies; and we may add to our description, in like manner, as many other qualities as there are various substances which produce in it any change, or are in any way changed by it. In all answers of this kind, you will perceive that regard is uniformly had, not to the mere substance, concerning which the question is put, but also to some other substance with which, in consequence of some motion of one or other of the bodies, at the time of the phenomenon of which we speak, it has changed its relative position; for, if all the objects in nature remained constantly at rest, it is very evident that we could have no notion of any property of matter whatever. In the enumeration of the qualities of glass, for example, when we speak of its properties, we suppose it to have changed, in every case, some relative position with the light that passes through it, the heat that melts it, the fluoric acid that dissolves it, and the various bodies that excite in it, or conduct from it, electricity; and all these bodies, therefore, we must have in view, in our enumeration, as much as the glass itself.

As there are only these two different aspects in which matter can be viewed, all physical inquiry, with respect to matter, must, as I have said, have reference to one of them; and if we think that we are inquiring further concerning it, our inquiry is truly without an object, and we know not what we seek. We may consider it, simply as it exists in space, or as it exists in time. Any substance, considered as it exists in space, is the mere name which ourselves give to the co-existence of a multitude of bodies, similar in nature, or dissimilar, in apparent continuity; considered as it exists in time, it is that which is affected by the prior changes of other bodies, or which itself produces a change of some sort in other bodies. As it exists in space, therefore, we inquire into its composition, or, in other words, endeavour to discover what are the elementary bodies that co-exist in the space which it occupies, and that are all which we truly consider, when we think that we are considering the compound as one distinct body. As it exists in time, we inquire into its susceptibilities or its powers, or, in other words, endeavour to trace all the series of prior and subsequent changes, of which its presence forms an intermediate link.

This, then, is our meaning, when we speak of inquiring into the nature of a substance. We have one, or both of two objects in view, the discovery of the separate bodies that co-exist in the substance, or rather that constitute the substance, which is nothing more than the separate bodies themselves, or the discovery of that series of changes, of which the presence of this particular substance, in some new relative position with respect to other bodies, forms a part; the changes which other bodies, in consequence of this altered relative position, occasion in it, with the changes which it occasions in other bodies.

On these two different objects of physical investigation, the co-existing elements of bodies, and their successions of changes, it may be of advantage to dwell a little more fully in elucidation of the method which we have to pursue in our own department of physical research; for, though it may perhaps at first appear to you, that to treat of the principles of inquiry, in the physics of matter, is to wander from the intellectual and moral speculations which peculiarly concern us; it is in truth only as they are illustrative of inquiries which we are to pursue in the physiology of the mind, that I am led to make these general remarks. The principles of philosophic investigation are, as I have already said, common to all the sciences. By acquiring more precise notions of the objects of any one of them, we can scarcely fail to acquire, in some degree, more precision in our notions of every other, and each science may thus be said to profit indirectly by every additional light that is thrown upon each. It is by this diffusive tendency of its spirit, almost as much as by its own sublime truths, and the important applications of these to general physics, that the study of geometry has been of such inestimable advantage to science. Those precise definitions which insure to every word the same exact signification, in the mind of every one who hears it pronounced, and that lucid progress in the developement of truth after truth, which gives, even to ordinary powers, almost the same facility of comprehension with the highest genius, are unquestionably of the utmost benefit to the mathematical student, while he is prosecuting his particular study, without any contemplation of other advantages to be reaped from them. But there can be no doubt that they are, at the same time, preparing his mind for excellence in other inquiries, of which he has then no conception; that he will ever after be less ready to employ, and be more quicksighted than he would otherwise have been in detecting vague and indefinite phraseology, and loose and incoherent reasoning; and that a general spirit of exactness and perspicuity may thus at length be diffused in society, which will extend its influence, not to the sciences merely, but, in some faint degree, also to works of elegant literature, and even to the still lighter graces of conversation itself. “The spirit of geometrical inquiry,” says Fontenelle, “is not so exclusively attached to geometry, as to be incapable of being applied to other branches of knowledge. A work of morals, of politics, of criticism, or even of eloquence, will, if all other circumstances have been the same, be the more beautiful, for having come from the hand of a geometrician. The order, the clearness, the precision, which, for a considerable time, have distinguished works of excellence on every subject, have most probably had their origin in that mathematical turn of thought, which is now more prevalent than ever, and which gradually communicates itself even to those who are ignorant of mathematics. It often happens that a single great man gives the tone to the whole age in which he lives; and we must not forget, that the individual who has the most legitimate claim to the glory of having introduced and established a new art of reasoning, was an excellent geometer.”22 The philosopher to whom this improvement of the art of reasoning is ascribed, is evidently Descartes, whose claim is certainly much less legitimate than that of our own illustrious countryman; but the works of Bacon were not very extensively studied on the continent, at the time at which Fontenelle wrote; while especially in France, the splendid reputation of the great geometer, who shook, as much with his own wild hypothesis, as with the weight of his reasoning, the almost idolatrous worship of the God of the Schools, seemed to sweep before it the glory of every other reformer. The instance of Descartes, however, is a still more happy one than his ingenious countryman, who was himself a Cartesian, could have imagined it to be. It is, indeed, impossible to conceive a more striking example of that diffusive influence of the general spirit of scientific inquiry, which I wish to illustrate; since, in this instance, it survived the very system by which it was diffused; all that was sceptical in that mixed system of scepticism and dogmatism which constituted the philosophy of Descartes, having long continued, and even now continuing, to operate beneficially, when scarcely a doctrine of his particular philosophy retains its hold.

You will not then, I trust, take for granted, that precise notions as to the objects of inquiry, in any science, even in the department of external physics, can be so absolutely without benefit to our plans of inquiry into mind, which must be pursued on the same principles, if it be pursued with any prospect of success; and I may, therefore, safely solicit your attention to a little farther elucidation of the two objects which we have in view, in general physical inquiry, whether it be relative to matter or to mind.

To inquire into the composition of a substance, is to consider as one, many substances, which have not the less an independent existence, because they are in immediate proximity to each other. What we term a body, however minute, is a multitude of bodies, or to speak more exactly, an infinite number of bodies, which appear limited to us, indeed, but may perhaps appear, in their true character of infinity, to beings of a higher order, who may be able to distinguish as infinite, what our limited senses allow us to perceive only as finite. They are one, not in nature, but in our thought; as one thousand individuals, that in nature must always be one thousand, receive a sort of unity that is relative merely to our conception, when ranked by us as a single regiment, or as many regiments become one by forming together an army. In the energies of external matter, the innumerable separate bodies are thus regarded by us as one, when the space which divides them is not measurable by our imperfect vision, and as distinct or separate, when the space can be measured by us. The unity of the aggregate is here no absolute quality of the mass, but is truly relative to the observer's power of distinguishing the component parts; the mass being one or many, as his senses are less or better able to distinguish these. This whole globe of earth, with its oceans, and rivers, and mountains, and woods, and with all the separate multitudes of its animated inhabitants, may seem to some being of another species, only one continuous and uniform mass; as the masses, that seem to us uniform and continuous, may seem a whole world of separate and varied parts, to the insect population that swarms upon its surface. “A single leaf of a tree,” to borrow an obvious illustration from a French writer, “is a little world inhabited by invisible animals, to whose senses it appears of immense extent, who see in it mountains and abysses that are almost immeasurable, and who, from one side of the leaf to the other, hold as little communication with the opposite animalcula, who have their dwellings there, as we do with our Antipodes.”23

Nothing can appear to our eyes more uniform than a piece of glass; yet we know, from its composition, as a product of art, that it is a congeries of bodies, which have no similarity to each other, and which truly exist separately from each other, in the compound, as they existed separately before the composition, though the lines of space which divide them have now ceased to be visible to our weak organs; and though, instead of being composed of alkaline and siliceous matter, which we know to be different in their qualities, the beautiful transparent substance, considered by us, were, as far as we know, simple, in the chemical sense of the term, it would still be as truly an aggregate of many bodies, not dissimilar, indeed, as in the former case, but each similar in qualities to the aggregate itself. The aggregate, in short, is, in every case, but a name invented by ourselves; and what we term the constituent elements, are all that truly exists. To inquire into the composition of a body, is, therefore, only to inquire what these separate bodies are which we have chosen to consider as one, or rather which are ranked by us as one, from their apparent continuity.

I have dwelt the longer on this point of the unity of an aggregate mass, as derived from the mind of the observer only, and not from its constituent bodies, which are truly separate and independent of each other, and must always be separate and independent, whatever changes they may seem to undergo, in the various processes of composition and decomposition, because this is one of the most simple, and, at the same time, one of the most convincing examples of a tendency of the mind, which we shall often have occasion to remark in the course of our intellectual analysis, – the tendency to ascribe to substances without, as if existing in them like permanent physical qualities, the relations which ourselves have formed, by the mere comparison of objects with objects, and which, in themselves, as relations, are nothing more than modifications of our own mind. It is very difficult for us to believe, that, when we speak of a rock, or a mountain, or, perhaps, still more, when we speak of a single leaf or blade of grass as one, we speak of a plurality of independent substances, which may exist apart, as they now exist together, and which have no other unity than in our conception. It is the same with every other species of relation. The tallness of a tree, the lowness of a shrub or weed, as these relative terms are used by us in opposition, do not express any real quality of the tree, or shrub, or weed, but only the fact that our mind has considered them together; all which they express, is the mere comparison that is in us, not any quality in the external objects; and yet we can scarcely bring ourselves to think, but that independently of this comparison, there is some quality, in the tree, which corresponds with our notion of tallness, and some opposite quality in the shrub or weed, which corresponds with our notion of shortness or lowness; so that the tree would deserve the name of tall, though it were the only object in existence, and the shrub or weed, in like manner, the epithet of lowly, though it alone existed, without a single object with which it could be compared. These instances, as I have said, are simple, but they will not be the less useful, in preparing your minds for considering the more important natures of relation in general, that imply, indeed, always some actual qualities in the objects themselves, the perception of which leads us afterwards to consider them as related, but no actual quality in either of the objects that primarily and directly corresponds with the notion of the relation itself, as there are qualities of objects that correspond directly with our sensations of warmth or colour, or any other of the sensations excited immediately by external things. The relation is, in every sense of the word mental, not merely as being a feeling of the mind, for our knowledge of the qualities of external things is, in this sense, equally mental; but, as having its cause and origin directly in the very nature of the mind itself, which cannot regard a number of objects, without forming some comparison, and investing them consequently with a number of relations. I have already spoken of the intellectual medium, through which external objects become known to us; and the metaphor is a just one. The medium, in this case, as truly as in the transmission of light, communicates something of its own to that which it conveys; and it is as impossible for us to perceive objects long or often together, without that comparison which instantly invests them with certain relations, as it would be for us to perceive objects, for a single moment, free from the tint of the coloured glass through which we view them. “Omnes perceptiones,” says Lord Bacon, using a similar figure, “omnes perceptiones, tam sensus quam mentis, sunt ex analogia hominis, non ex analogia universi; estque intellectus humanus instar speculi inæqualis ad radios rerum, qui suam naturam naturæ rerum immiscet, eamque distorquet et inficit.”

But, whatever may be thought of relations in general, there can be no question, at least, as to the nature of that unity which we ascribe to bodies. We have seen, that the substance, which, in thought we regard as one, is, in truth, not one, but many substances, to which our thought alone gives unity; and that all inquiry, therefore, with respect to the nature of a substance, as it exists in space, is an inquiry into the nature of those separate bodies, that occupy the space which we assign to the imaginary aggregate.

To dissipate this imaginary aggregate of our own creation, and to show us those separate bodies which occupy its space, and are all that nature created, is the great office of the analytic art of Chemistry, which does for us only what the microscope does, that enables us to see the small objects which are before us at all times, without our being able to distinguish them. When a chemist tells us, that glass, which appears to us one uniform substance, is composed of different substances, he tells us, what, with livelier perceptive organs, we might have known, without a single experiment; since the siliceous matter and the alkali were present to us in every piece of glass, as much before he told us of their presence, as after it. The art of analysis, therefore, has its origin in the mere imperfection of our senses, and is truly the art of the blind, whose wants it is always striving to remedy, and always discovering sufficient proof of its inability to remedy them.

We boast, indeed, of the chemical discoveries which we have made of late, with a rapidity of progress as brilliant, as it is unexampled in the history of any other science; and we boast justly, because we have found, what the generations of inquirers that have preceded us on our globe, – far from detecting, – had not even ventured to guess. Without alluding to the agency of the Galvanic power, – by which all nature seems to be assuming before us a different aspect – we have seen fixed in the products of our common fires, and in the drossy rust of metals, the purest part of that ethereal fluid which we breathe, and the air itself, which was so long considered as simple, ceasing to be an element. Yet whatever unsuspected similarities and diversities of composition we may have been able to trace in bodies, all our discoveries have not created a single new particle of matter. They have only shown these to exist, where they always existed, as much before our analysis as after it, – unmarked indeed, but unmarked, only because our senses alone were not capable of making the nice discrimination. If man had been able to perceive, with his mere organs of sense, the different particles that form together the atmospheric air – if he had at all times seen the portion of these which unites with the fuel that warms him, enter into this union, as distinctly as he sees the mass of fuel itself, which he flings into his furnace, he could not have thought it a very great intellectual achievement, to state in words so common and familiar a fact, – the mere well-known change of place of a few well-known particles; and yet this is what, in the imperfect state of his perceptive organs, he so proudly terms his Theory of Combustion, the developement of which was hailed by a wondering world, and in these circumstances justly hailed by it, as a scientific era. To beings, capable of perceiving and distinguishing the different particles, that form by their aggregation, those small masses, which, after the minutest mechanical division of which we are capable, appear atoms to us, the pride which we feel, in our chemical analyses, must seem as ludicrous, as to us would seem the pride of the blind, if one, who had never enjoyed the opportunity of beholding the sun, were to boast of having discovered, by a nice comparison of the changing temperature of bodies, that, during certain hours of the day, there passed over our earth some great source of heat. The addition of one new sense to us, who have already the inestimable advantages which vision affords, might probably, in a few hours, communicate more instruction, with respect to matter, than all which is ever to repay and consummate the physical labours of mankind, – giving, perhaps, to a single glance, those slow revelations of nature, which, one by one, at intervals of many centuries, are to immortalize the future sages of our race.