material substances whatever, the only difference being that the energies by which their molecules are held together are so held under conditions which are more stable-conditions which it is much more difficult to change-and conditions, therefore, which conceal from us the universal prevalence and power of force in the constitution of the material universe. It is, therefore, distinctly the tendency of science more and more to impress us with the idea of the unlimited duration and indestructible nature both of matter and of the energies which work in and upon it. One of the scientific forms under which this idea is expressed is the conservation of energy. It affirms that though we often see moving bodies stopped in their course, and the energy with which they move apparently extinguished, no such extinction is really effected. It affirms that this energy is merely transformed into other kinds of notion which may or may not be visible, but which, whether visible or not, do always really survive the motion which has been arrested. It affirms, in short, that energy, like matter, cannot be destroyed or lessened in quantity, but can only be redistributed. As, however, the whole existing order of nature depends on very special distributions and concentrations of force, this doctrine affords no ground for presuming on the permanence, or even on the prolonged continuance, of that order. Quite the contrary; for another general conception has been attained from science which at first sight appears to be a contradiction of the doctrine of Conservation of Energy namely, the "Dissipation of Energy." This doc trine, however, does not affirm that energy can be dissipated in the sense of being wholly lost or finally extinguished. It only affirms that all the existing concentrations of force are being gradually exhausted, and that the forces concerned in them are being diffused generally in the form of heat) more and more equally over the infinitudes of matter and of space. Closely connected with, if indeed it be not a necessary part and consequence of, these conceptions of the infinity of space and time, of matter and of force, is the more general concept of causation. All at It is impossible to conceive of anything happening without a cause. Even if we could conceive the utter destruction or annihilation of any particular force or form of force, we cannot conceive of this very destruction happening except as the effect of some cause. tempts to reduce this idea of causation to other and lower terms have been worse than futile. They have uniformly left out something which is of the very essence of the idea. The notion of "uniform antecedence" is. not equivalent. "Necessary antecedence" is more near the mark. These words do indeed indicate the essential element in the idea with tolerable clearness. But, like all other simple fundamental conceptions, the idea of causation defies analysis. As, however, we cannot dissociate the idea of causation from the idea of force or energy, it may, perhaps, be said that the indestructibility or eternal duration of force is a physical doctrine which gives strength and substance to the metaphysical concept of causation. Science may discover, and indeed has already discovered, that as regards our application of the idea of cause, and of the correlative idea of effect, to particular cases of sequence, there is often some apparent confusion arising from the fact that the relative positions of cause and effect inay be interchangeable, so that A, which at one moment appears as the cause of B, becomes at another moment the consequence of B, and not its cause. Thus heat is very often the cause of visible motion, and visible motion is again the cause of heat. And so of the whole cycle of physical forces, which Sir W. Grove and others have proved to be "correlated"-that is, to be so intimately related that each may in turn produce or pass into all the others. But this does not really obscure or cast any doubt upon the truth of our idea of causation. On the contrary, that idea is confirmed in receiving a new interpretation, and in the disclosure of physical facts involving the same conception. The necessity of the connection between an effect and its cause receives an unexpected confirmation when it comes to be regarded as simply the necessary passing of an energy which is universal and indestructible from one form of action into another. Heat becomes the cause 66 of light because it is the same energy working in a special medium. Conversely light becomes the cause of heat, because again the same energy passes into another medium and there produces a different effect. And so all the socalled correlated forces' may be interchangeably the cause or the consequence of each other, according to the order of time in which the changes of form are seen. This, however, does not confound, but only illustrates the ineradicable conviction that for all such changes there must be a cause. It may be perfectly true that all these correlated forces can be ideally reduced to different forms of motion;" but motion itself is inconceivable except as existing in matter, and as the result of some moving orce. Every difference of direction in motion or of form in matter implies a change, and we can conceive no change without a cause-that is to say, apart from the operation of some condition without which that change would not have been. The same ultimate conceptions, and no other, appear to constitute all the truth that is to be found in a favorite doctrine among the cultivators of physical science the so-called "Law of Continuity. This phrase is indeed often used with such looseness of meaning that it is extremely difficult to understand the primary signification attached to it. One common definition, or rather one common illustration, of this law is said to be that nature does nothing suddenly-nothing "per sal tum." Of course this can only be accepted under soine metaphorical or transcendental meaning. In nature there is such a thing as a flash of lightning, and this is generally recognized as sufficiently sudden. A great many other exertions of electric force are of similar rapidity. The action of chemical affinity is always rapid, and very often even instantaneous. Yet these are among the most common and the most powerful factors in the mechanism of nature. They have the most intimate connection with the phenomena of life, and in these the profoundest changes are often determined in moments of time. For many purposes to which this so-called "Law of Continuity" is often applied in argument no idler dogma was There is ever invented in the schools. a common superstition that this so-called law negatives the possibility, for example, of the sudden appearance of new forms of life. What it does negative, however, is not appearances which are sudden, but only appearances which have been unprepared. Innumerable things may come to be-in a momentin the twinkling of an eye. But nothing can come to be without a long, even if it be a secret, history. The "Law of Continuity" is, therefore, a phrase of ambiguous meaning; but at the bottom. of it there lies the true and invincible conviction that for every change, however sudden-for every "leap, however wide-there has always been a long chain of predetermining causes, and that even the most tremendous bursts of energy and the most sudden exhibitions of force have all been slowly and silently prepared. In this sense the law of continuity is nothing but the idea of causation. It is founded on the necessary duration which we cannot but attribute to the existence of force, and this appears to be the only truth which the law of continuity represents. When now we consider the place in the whole system of our knowledge which is occupied by these great fundamental conceptions of time and space, and of matter and of force, and when we consider that we cannot even think of any one of these realities as capable of coming to an end, we may well be assured that, whatever may be the limits of the human mind, they certainly do not prevent us from apprehending infinity. On the contrary, it would rather appear that this apprehension is the invariable and necessary result of every investigation of nature. It is indeed of the highest importance to observe that some of these conceptions, especially the indestructibility of matter and of force, belong to the domain of science. That is to say, the systematic examination of natural phenomena has given them distinctness and a consistency which they never possessed before. As now accepted and defined, they are the result of direct experiment. And yet, strictly speaking, all that experiment can do is to prove that in all the cases in which either matter or force seems to be destroyed no such destruc 66 tion has taken place. Here, then, we have a very limited and imperfect amount of experience" giving rise to an infinite conception. But it is another of the suggestions of the Agnostic philosophy that this can never be a legitimate result. Nevertheless, as a matter of fact, these conceptions have been reached. They are now universally accepted and taught as truths lying at the foundation of every branch of natural science-at once the beginning and the end of every physical investigation. They are not what are ordinarily called “laws.” They stand on much higher ground. They stand behind and before every law, whether that word be taken to mean simply an observed order of facts, or some particular force to which that order is due, or some combinations of force for the discharge of function, or some abstract definition of observed phenomena such as the "laws of motion." All these, though they may be "invariable" so far as we can see, carry with them no character of universal or necessary truth-no conviction that they are and must be true in all places and for all time. There is no existing order-no present combinations of matter or of force-which we cannot conceive coming to an end. But when that end is come we cannot conceive but that something must remain, if it be nothing else than that by which the ending was brought about, or, as it were, the raw materials of the creation which has passed away. That this conception, when once suggested and clearly apprehended, cannot be eradicated, is one of the most indisputable facts of instructed consciousness. That no possible amount of mere external observation or experiment can cover the infinitude of the conclusion is also unquestionably true. But if "experience" is to be upheld as in any sense the ground and basis of all our knowledge, it must be understood as embracing that most important of all kinds of experience in the study of nature-the experience we have of the laws of mind. It is one of the most certain of those laws that in proportion as the powers of the understanding are well developed, and are prepared by previous training for the interpretation of natural facts, there is no relation whatever be tween the time occupied in the observation of phenomena and the breadth or sweep of the conclusions which may be arrived at from them. A single glance, lasting not above a moment of time, may awaken the recognition of truths as wide as the universe and as everlasting as time itself. Nay, it has often happened in the history of science that such recognitions of general truths have been reached by no other kind of observation than that of the mind becoming conscious of its own innate perceptions. Conceptions of this nature have perpetually gone before experiment-have suggested it, guided it, and have received nothing more than corroboration from it. I do not say that these conceptions have been reached without any process. But the process has been to a large extent as unconscious as that by which we see the light. I do not say they have been reached without "experience," even in that narrow sense in which it means the observation of external things. But the experience has been nothing more than the act of living in the world, and of breathing in it, and of looking round upon it. These conceptions have come to man because he is a being in harmony with surrounding nature. The human mind has opened to them as a bud opens to the sun and air. So true is this that when reasons have been given for the conclusions thus arrived at-these reasons have often been quite erroneous. Nothing in the history of philosophy is more curious than the close correspondence between many ideas enunciated by the ancients as the result of speculation, and some, at least, of the ideas now prevalent as the result of science. It is true that the ancients expressed them vaguely, associated them with other conceptions which are wide of the truth, and quoted in support of them illustrations which are often childNevertheless, the fact remains that they had attained to some central truths, however obscured the perception may have been by ignorance of the more precise and accurate analogies by which they can be best explained, and which only the process of observation has revealed. They had in some way grasped," says Mr. Balfour Stewart, ish. * "Conservation of Energy," p. 135. * "the idea of the essential unrest and energy of things. They had also the idea of small particles or atoms; and finally of a medium of some sort, so that they were not wholly ignorant of the most profound and deeply-seated of the principles of the material universe." There is but one explanation of this, but it is all-sufficient. It is that the mind of man is a part, and one at least of the highest parts, of the system of the universe-the result of mechanism most suited to the purpose of catching and translating into thought the light of truth as embodied in surrounding nature. We have seen that the foundations of all conscious reasoning are to be found in certain propositions which we call self-evident. That is to say, in propositions the truth of which is intuitively perceived. We have seen, too, as a general law affecting all manifestations of life or mind, even in its very lowest forms, that instinctive or intuitional perceptions are the guide and index of other and larger truths which lie entirely beyond the range of the perception or intuition which is immediately concerned. This law holds good quite as much of the higher intuitions which are peculiar to man as of the mere intuitions of sensation which are common to him and to the animals beneath him. The lowest savage does many things by mere instinct which contain implicitly truths of a very abstract nature-truths of which, as such, he has not the remotest conception, and which in the present undeveloped condition of his faculties it would be impossible to explain to him. Thus, when he goes into the forest to cut a branch fit for being made into a bow, or when he goes to the marsh to cut a reed fit for being made into an arrow, and when in doing so he cuts them off the proper length by measuring them by the bows and arrows which he already has, in this simple operation he is acting on the abstract and most fruitful truth that things equal to the same thing are equal to one another." This is one of the axioms which lie at the basis of all mathematical demonstration. But as a general, universal, and necessary truth the savage knows nothing of it—as little as he knows of the wonderful conse quences to which it will some day lead his children or descendants. So in like manner when the savage designs, as he often does, most ingenious traps for the capture of his prey, and so baits them as to attract the animals he desires to catch, he is counting first on the constancy and uniformity of physical causation, and, secondly, on the profoundly different action of the motives which determine the conduct of creatures having life and will. But of neither of these as general truths does he know anything, and of one of them at least not even the greatest philosophers have reached the full depth or meaning. Nevertheless, it would be a great error to suppose that the savage, because he has no conception of the general truth involved in his conduct, has been guided in that conduct by any thing in the nature of chance or accident. His intuitions have been right, and have involved so much perception of truth as is necessary to carry him along the little way he requires to travel, because the mind in which those intuitions lie is a product and a part of nature-a product and part of that great system of things which is held together by laws intelligible to mind-laws which the human mind has been constructed to feel even when it cannot clearly see. Moreover, when these laws come to be clearly seen, they are seen only because the mind has organs adjusted to the perception of them, and because it finds in its own mechanism corresponding sequences of thought. It was the work of a great German metaphysician toward the close of the last century to discriminate and define more systematically than had been done before some at least of those higher elements of thought which, over and above the mere perception of external things, the mind thus contributes out of its own structure to the fabric of knowledge. In doing this he did immortal service--proving that when men talked of "* experience" being the source of knowledge they forgot that the whole process of experience presupposes the action of innate laws of thought, without which experience can neither gather its facts nor reach their interpretation. "Experience, as Kant most truly said, is nothing but a "synthesis of intuitions"--a building up or putting together of conceptions which the access of external nature finds ready to be awakened in the mind. The whole of this process is determined by the mind's own laws-a process in which even observation of outward fact must take its place according to principles of arrangement in which alone all explanation of them consists, and out of which any understanding of them is impossible. And yet this great fact of a large part of our knowledge-and that the most important part-coming to us out of the very furniture and constitution of the mind itself, has been so expressed and presented in the language of philosophy as rather to undermine than to establish our confidence in the certainty of knowledge. For if the mind is so spoken of and represented as to suggest the idea of something apart from the general system of nature, and if its laws of thought are looked upon as "forms" or moulds into which, by some artificial arrangement or by some mechanical necessity, everything from outside must be squeezed and made to fit-then it will naturally occur to us to doubt whether conceptions cut out and manufactured under such conditions can be any trustworthy representation of the truth. Such, unfortunately, has been the mode of representation adopted by many philosophers and such accordingly has been the result of their teaching. This is the great source of error in every form of the idealistic philosophy, but it is a source of error which can be perfectly eliminated, leaving untouched and undoubted the large body of truths which has made that philosophy attractive to so many powerful minds. We have only to take care that in expressing those truths we do not use metaphors which are misleading. We have only to remember that we must regard the mind and the laws of its operation in the light of that most assured truth-the unity of nature. The mind has no "moulds" which have not themselves been moulded on the realities of the universe-no "forms" which it did not receive as a part and a consequence of a unity with the rest of nature. Its conceptions are not manufactured; they are developed. They are not made; they simply grow. The order of the laws of thought under which it renders intelligible to itself all the phenomena of the universe is not an order which it invents, but an order which it simply feels and sees. And this "vision and faculty divine is a necessary consequence of its congenital relations with the whole system of nature-from being bone of its bone-flesh of its flesh-from breathing its atmosphere, from living in its light, and from having with it a thousand points of contact visible and invisible, more than we can number or understand. And yet so subtle are the suggestions of the human spirit in disparagement of its own powers so near and ever-present to us is that region which belongs to the unsatisfied reserve of power-that the very fact of our knowledge arising out of our organic relations with the rest of nature has been seized upon as only casting new discredit on all that we seem to know. Because all our knowledge arises out of these relations, therefore, it is said all our knowledge of things must be itself relative; and relative knowledge is not knowledge of "things in themselves." Such is the argument of metaphysicians-an argument repeated with singular unanimity by philosophers of almost every school of thought. By some it has been made the basis of religious proof. By some it has been made the basis of a reasoned scepticism. By others it has been used simply to foil attacks upon belief. The real truth is that it is an argument useless for any purpose whatever, because it is not itself true. The distinction between knowledge of things in their relations and knowledge of things "in themselves' is a distinction without a meaning. In metaphysics the assertion that we can never attain to any knowledge of things in themselves does not mean simply that we know things only in a few relations out of many. It does not mean even that there may be and probably are a great many relations which we have not faculties enabling us to conceive. All this is quite true, and a most important truth. But the metaphysical distinction is quite different. It affirms that if we knew things in every one of the relations that affect them we should still be no nearer than before to a knowledge of "things in themselves." "It is |