The founder of the realistic course and the father of modern Empiricism and Materialism, is John Locke, an Englishman. Thomas Hobbes (1588-1679) was his predecessor and countryman, whose name we need here only mention, as it has no importance except for the history of natural rights.

John Locke was born at Wrington, 1632. His student years he devoted to philosophy and prominently to medicine, though his weak health prevented him from practising as a physician. Few cares of business interrupted his leisure, and he devoted his time mostly to literary pursuits. His friendly relations with Lord Anthony Ashley, afterwards Earl of Shaftesbury, exerted a weighty influence upon his course in life. At the house of this distinguished statesman and author he always found the most cordial reception, and an intercourse with the most important men of England. In the year 1670 he sketched for a number of friends the first plan of his famous Essay on the Human Understanding, though the completed work did not appear till 1689. Locke died aged 72 in the year 1704. His writings are characterized by clearness and precision, openness and determinateness. More acute than profound in his philosophizing, he does not in this respect belie the characteristic of his nation. The fundamental thoughts and results of his philosophy have now become common property, especially among the English, though it should not therefore be forgotten that he is the first who has scientifically established them, and is, on this account, entitled to a true place in the history of philosophy, even though his principle was wanting in an inner capacity for development.

Locke’s Philosophy (i. e. his theory of knowledge, for his whole philosophizing expends itself in investigating the faculty of knowing) rests upon two thoughts, to which he never ceases to revert: first (negatively), there are no innate ideas; second (positively), all our knowledge arises from experience.

Many, says Locke, suppose that there are innate ideas which the soul receives coetaneous with its origin, and brings with it into the world. In order to prove that these ideas are innate, it is said that they universally exist, and are universally valid with all men. But admitting that this were so, such a fact would prove nothing if this universal harmony could be explained in any other way. But men mistake when they claim such a fact. There is, in reality, no fundamental proposition, theoretical or practical, which would be universally admitted. Certainly there is no such practical principle, for the example of different people as well as of different ages shows that there is no moral rule universally admitted as valid. Neither is there a theoretical one, for even those propositions which might lay the strongest claim to be universally valid, e. g. the proposition,—“what is, is,” or—“it is impossible that one and the same thing should be and not be at the same time,”—receive by no means a universal assent. Children and idiots have no notion of these principles, and even uncultivated men know nothing of these abstract propositions. They cannot therefore have been imprinted on all men by nature. If ideas were innate, then they must be known by all from earliest childhood. For “to be in the understanding,” and “to become known,” is one and the same thing. The assertion therefore that these ideas are imprinted on the understanding while it does not know it, is hence a manifest contradiction. Just as little is gained by the subterfuge, that these principles come into the consciousness so soon as men use their reason. This affirmation is directly false, for these maxims which are called universal come into the consciousness much later than a great deal of other knowledge, and children, e. g. give many proofs of their use of reason before they know that it is impossible that a thing should be and at the same time not be. It is only correct to say that no one becomes conscious of these propositions without reasoning,—but to say that they are all known with the first reasoning is false. Moreover, that which is first known is not universal propositions, but relates to individual impressions. The child knows that sweet is not bitter long before he understands the logical proposition of contradiction. He who carefully bethinks himself, will hesitate before he affirms that particular dicta as “sweet is not bitter,” are derived from universal ones. If the universal propositions were innate, then must they be the first in the consciousness of the child; for that which nature has stamped upon the human soul must come into consciousness antecedently to any thing which she has not written there. Consequently, if there are no innate ideas, either theoretical or practical, there can be just as truly no innate art nor science. The understanding (or the soul) is essentially a tabula rasa,—a blank and void space, a white paper on which nothing is written.

How now does the understanding become possessed of ideas? Only through experience, upon which all knowledge rests, and on which as its principle all knowledge depends. Experience itself is twofold; either it arises through the perception of external objects by means of the sense, in which case we call it sensation; or it is a perception of the activities of our own understanding, in which case it is named the inner sense, or, better, reflection. Sensation and reflection give to the understanding all its ideas; they are the windows through which alone the light of ideas falls upon the naturally dark space of the mind; external objects furnish us with the ideas of sensible qualities, and the inner object, which is the understanding itself, offers us the ideas of its own activities. To show the derivation and to give an explanation of all the ideas derived from both is the problem of the Lockian philosophy. For this end Locke divides ideas (representations or notions) into simple and compound. Simple ideas, he names those which are impressed from without upon the understanding while it remains wholly passive, just as the images of certain objects are represented in a mirror. These simple ideas are partly such as come to the understanding through an individual sense, e. g. the ideas of color, which are furnished to the mind through the eye, or those of sound, which come to it through the ear, or those of solidity or impenetrability, which we receive through the touch; partly such as a number of senses have combined to give us, as those of space and of motion, of which we become conscious by means of the sense both of touch and of sight; partly such as we receive through reflection, as the idea of thought and of will; and partly, in fine, such as arise from both sensation and reflection combined, e. g. power, unity, &c. These simple ideas form the material, as it were the letters of all our knowledge. But now as language arises from a manifold combination of letters, syllables and words, so the understanding forms complex ideas by the manifold combination of simple ideas with each other. The complex ideas may be referred to three classes, viz.: the ideas of mode, of substance, and of relation. Under the ideas of mode, Locke considers the modifications of space (as distance, measurement, immensity, surface, figure, &c.), of time (as succession, duration, eternity), of thought (perception, memory, abstraction, &c.), of number, power, &c. Special attention is given by Locke to the conception of substance. He explains the origin of this conception in this way, viz.: we find both in sensation and reflection, that a certain number of simple ideas seem often to be connected together. But as we cannot divest ourselves of the impression that these simple ideas have not been produced through themselves, we are accustomed to furnish them with a ground in some existing substratum, which we indicate with the word substance. Substance is something unknown, and is conceived of as possessing those qualities which are necessary to furnish us with simple ideas. But from the fact that substance is a product of our subjective thinking, it does not follow that it has no existence outside of ourselves. On the contrary, this is distinguished from all other complex ideas in the fact that this is an idea which has its archetype distinct from ourselves, and possesses objective reality, while other complex ideas are formed by the mind at pleasure, and have no reality corresponding to them external to the mind. We do not know what is the archetype of substance, and of the substance itself we are acquainted only with its attributes. From considering the conception of substance, Locke next passes over to the idea of relation. A relation arises when the understanding has connected two things with each other, in such a way, that in considering them it passes over from the one to the other. Every thing is capable of being brought by the understanding into relation, or what is the same thing, to be transformed into something relative. It is consequently impossible to enumerate the sum of every possible relation. Hence Locke treats only of some of the more weighty conceptions of relation, among others, that of identity and difference, but especially that of cause and effect. The idea of cause and effect arises when our understanding perceives that any thing whatsoever, be it substance or quality, begins to exist through the activity of another. So much concerning ideas. The combination of ideas among themselves gives the conception of knowing. Hence knowledge stands in the same relation to the simple and complex ideas as a proposition does to the letters, syllables and words which compose it. From this it follows that our knowledge does not pass beyond the compass of our ideas, and hence that it is bounded by experience.

These are the prominent thoughts in the Lockian philosophy. Its empiricism is clear as day. The mind, according to it, is in itself bare, and only a mirror of the outer world,—a dark space which passively receives the images of external objects; its whole content is made by the impressions furnished it by material things. Nihil est in intellectu, quod non fuerit in sensu—is the watchword of this standpoint. While Locke, by this proposition, expresses the undoubted preponderance of the material over the intellectual, he does so still more decisively when he declares that it is possible and even probable that the mind is a material essence. He does not admit the reverse possibility, that material things may be classed under the intellectual as a special kind. Hence with him mind is the secondary to matter, and hence he is seen to take the characteristic standpoint of realism (cf. § XXVII). It is true that Locke was not always logically consistent, and in many points did not thoroughly carry out his empiricism: but we can clearly see that the road which will be taken in the farther development of this direction, will result in a thorough denial of the ideal factor.

The empiricism of Locke, wholly national as it is, soon became the ruling philosophy in England. Standing on its basis we find Isaac Newton, the great mathematician (1642-1727), Samuel Clarke, a disciple of Newton, whose chief attention was given to moral philosophy (1675-1729), the English moralists of this period, William Wollaston (1659-1724), the Earl of Shaftesbury (1671-1713), Francis Hutcheson (1694-1746), and even some opponents of Locke, as Peter Brown, who died 1735.