of matter,” and the others “secondary or derived qualities.” The
primary, which are quantities rather than qualities, are inseparable
from matter, and virtually identical with the ideas we have of them.
On the other hand, there is nothing perceived in the mathematical
relations of bodies which in the least resembles their secondary
qualities. If there were no sentient beings in existence, the secondary
qualities would cease to exist, “except perhaps as unknown modes
of the primary, or, if not, as something still more obscure.” On the
other hand, “solidity, extension, figure and motion would,” he
assumes, “be really in the world as they are, whether there were any
sensible being to perceive them or not.”
Thus far the outcome of what Locke teaches about matter is, that it is Something capable of being expressed in terms of mathematical quantity, and also in terms of our own sensations. A further step was to suggest the ultimate dependence of the secondary qualities of bodies upon “the bulk, figures, number, Matter. situation and motions of the solid parts of which the bodies consist,” these mathematical or primary qualities “existing as we think of them whether or not they are perceived.” This Locke proposes in a hesitating way. For we, “not knowing what particular size, figure and texture of parts they are on which depend, and from which result, those qualities which make our complex idea, for example, of gold, it is impossible we should know what other qualities result from, or are incompatible with, the same constitution of the insensible parts of gold; and so consequently must always coexist with that complex idea we have of it, or else are inconsistent with it.”
Some of the most remarkable chapters in the second book concern what may be called “crucial instances” in verification of its fundamental hypothesis of the dependence of human knowledge upon the simple ideas presented in our dual experience (bk. ii. ch. 13-28). They carry us towards the ultimate mysteries which attract meditative minds. The hypothesis, that even our most profound and sublime speculations are all limited to data of the senses and of reflection, is crucially tested by the “modes” and “substances” and “relations” under which, in various degrees of complexity, we somehow find ourselves obliged to conceive those simple phenomena. Such are modes of quantity in space, and time and number, under which Locke reports that we find ourselves mentally impelled towards immensity, eternity and the innumerable—in a word, towards Infinity which seems to transcend quantity; then there is the complex thought of Substance, to which we find ourselves mysteriously impelled, when the simple phenomena of the senses come to be regarded as qualities of “something”; again there is the obscure idea of the identity of persons, notwithstanding their constant changes of state; and there is, above all, the inevitable tendency we somehow have to refund a change into what we call its “Cause,” with the associated idea of active power. Locke begins with our complex ideas of Space, Succession or Time, and Number.
Space, he says, appears when we use our senses of sight and touch; succession he finds “suggested” by all the changing phenomena of sense, and by “what passes in our minds”; number is “suggested by every object of our senses, and every thought of our minds, by everything that either doth Immensity and endlessness and infinity. exist or can be imagined.” The modifications of which these are susceptible he reports to be “inexhaustible and truly infinite, extension alone affording a boundless field to the mathematicians.” But the mystery latent in our ideas of space and time is, that “something in the mind” irresistibly hinders us from allowing the possibility of any limit to either. We find ourselves, when we try, compelled to lose our positive ideas of finite spaces in the negative idea of Immensity or Boundlessness, and our positive ideas of finite times in the negative thought of Endlessness. We have never seen, and we cannot imagine, an object whose extent is boundless. Yet we find when we reflect that something forces us to think that space and time must be unlimited. Thus Locke seems by implication to acknowledge something added by the mind to the original “simple ideas” of extension and succession; though he finds that what is added is not positively conceivable. When we reflect on immensity and eternity, we find them negations of all that is imaginable; and that whether we try infinite addition or infinite subdivision. He accepts this fact; he does not inquire why mind finds itself obliged to add without limit and to divide without limit. He simply reports that immensity and eternity are inevitable negative ideas, and also that every endeavour to realize them in positive images must be an attempt to represent as quantity what is beyond quantity. After all our additions we are as far from the infinite idea as we were at the beginning.
Locke is too faithful to facts to overlook the ultimate mysteries in human experience. This is further illustrated in his acknowledgment of the inconceivable that is at the root of our idea of Substance. He tries to phenomenalize it, and thus resolve it into simple ideas; but he finds that it cannot be Substance and personality. phenomenalized, and yet that we cannot dispense with it. An unsubstantiated succession of phenomena, without a centre of unity to which they are referable as qualities, is unintelligible: we cannot have a language of adjectives without nouns. Locke had some apprehension of this transcendent intellectual obligation. According to his report, “the mind” always obliges us to suppose Something beyond positive phenomena to which the phenomena must be attributed; but he was perplexed by this “confused negative” idea. So for him the word substance means “only an uncertain supposition of we know not what.” If one were to ask him what the substance is in which this colour and that taste or smell inhere, “he would find himself in a difficulty like that of the Indian, who, after saying that the world rested on an elephant, and the elephant on a broad-backed tortoise, could only suppose the tortoise to rest on ‘Something, I know not what.’ ” The attempt to conceive it is like the attempt positively to conceive immensity or eternity: we are involved in an endless, ultimately incomprehensible, regress. We fail when we try either positively to phenomenalize substance or to dispense with the superphenomenal abstraction. Our only positive idea is of an aggregate of phenomena. And it is only thus, he says, that we can approach a positive conception of God, namely by “enlarging indefinitely some of the simple ideas we received from reflection.” Why man must remain in this mental predicament, Locke did not inquire. He only reported the fact. He likewise struggled bravely to be faithful to fact in his report of the state in which we find ourselves when we try to conceive continued personal identity. The paradoxes in which he here gets involved illustrate this (bk. ii. ch. 27).
Locke’s thoughts about Causality and Active Power are especially noteworthy, for he rests our knowledge of God and of the external universe on those ultimate ideas. The intellectual demand for “the cause” of an event is what we find we cannot help having; yet it is a demand for what in the end the mind cannot Causality. fully grasp. Locke is content to trace the idea of “cause and effect,” as far as mere natural science goes, to our “constant observation” that “qualities and finite substances begin to exist, and receive their existence from other beings which produce them.” We find that this connexion is what gives intelligibility to ceaseless and what seemed chaotic changes, converting them into the divinely concatenated system which we call “the universe.” Locke seems hardly to realize all that is implied in scientific prevision or expectation of change. Anything, as far as “constant observation” tells us, might a priori have been the natural cause of anything; and no finite number of “observed” sequences, per se, can guarantee universality and necessity. The idea of power, or active causation, on the other hand, “is got,” he acknowledges, not through the senses, but “through our consciousness of our own voluntary agency, and therefore through reflection” (bk. ii. ch. 21). In bodies we observe no active agency, only a sustained natural order in the succession of passive sensuous phenomena. The true source of change in the material world must be analogous to what we are conscious of when we exert volition. Locke here unconsciously approaches the spiritual view of active power in the physical universe afterwards taken by Berkeley, forming the constructive principle of his philosophy.
Locke’s book about Ideas leads naturally to his Third Book which is concerned with Words, or the sensible signs of ideas. Here he analyses “abstract ideas,” and instructively illustrates the confusion apt to be produced in them by the inevitable imperfection of words. He unfolds the relations between Ideas and words. verbal signs and the several sorts of ideas; words being the means for enabling us to treat ideas as typical, abstract and general. “Some parts of this third book,” concerning Words, Locke tells his friend Molyneux, “though the thoughts were easy and clear enough, yet cost me more pains to express than all the rest of my Essay. And therefore I should not much wonder, if there be in some places of it obscurity and doubtfulness.”
The Fourth Book, about Knowledge proper and Probability, closes the Essay. Knowledge, he says, is perception of relations among ideas; it is expressed in our affirmations and negations; and real knowledge is discernment of the relations of ideas to what is real. In the foregoing part Theory of knowledge. of the Essay he had dealt with “ideas” and “simple apprehension,” here he is concerned with intuitive “judgment” and demonstrative “reasoning,” also with judgments and reasonings about matters of fact. At the end of this patient search among our ideas, he supposes the reader apt to complain that he has been “all this while only building a castle in the air,” and to ask what the purpose of all this stir is, if we are not thereby carried beyond mere ideas. “If it be true that knowledge lies only in the agreement or disagreement of ideas, the visions of an enthusiast and the reasonings of a sober man will be equally certain. It is no matter how things themselves are” (bk. iv. 4). This gives the keynote to the fourth book. It does not, however, carry him into a critical analysis of the rational constitution of knowledge, like Kant. Hume had not yet shown the sceptical objections against conclusions which Locke accepted without criticism. The subtle agnostic, who doubted reason because reason could not be supported in the end by empirical evidence, was less in his view than persons blindly resting on authority or prejudice. Total scepticism he would probably have regarded as unworthy of the serious attention of a wise man. “Where we perceive the agreement or disagreement of any of our ideas there is certain knowledge; and wherever we are sure these ideas agree with the reality of things, there is certain real knowledge” (bk. iv. ch. 4).
Locke’s report about human knowledge and its narrow extent forms the first thirteen chapters of the fourth book. The remainder of the book is concerned for the most part with the probabilities on which human life practically turns, as he and Butler are fond of
