Clearer upon this question of perception is the position of Berkeley; we may therefore take him as a fair representative of those critics who seek to invalidate the discovery of material objects.
Berkeley's algebra of perception.
Our ideas, said Berkeley, were in our minds; the material world was patched together out of our ideas; it therefore existed only in our minds. To the suggestion that the idea of the external world is of course in our minds, but that our minds have constructed it by treating sensations as effects of a permanent substance distributed in a permanent space, he would reply that this means nothing, because "substance," "permanence," and "space" are non-existent ideas, i.e., they are not images in sense. They might, however, be "notions" like that of "spirit," which Berkeley ingenuously admitted into his system, to be, mysteriously enough, that which has ideas. Or they might be (what would do just as well for our purpose) that which he elsewhere called them, algebraic signs used to facilitate the operations of thought. This is, indeed, what they are, if we take the word algebraic in a loose enough sense. They are like algebraic signs in being, in respect of their object or signification, not concrete images but terms in a mental process, elements in a method of inference. Why, then, denounce them? They could be used with all confidence to lead us back to the concrete values for which they stood and to the relations which they enabled us to state and discover. Experience would thus be furnished with an intelligible structure and articulation, and a psychological analysis would be made of knowledge into its sensuous material and its ideal objects. What, then, was Berkeley's objection to these algebraic methods of inference and to the notions of space, matter, independent existence, and efficient causality which these methods involve?
Horror of physics.
What he abhorred was the belief that such methods of interpreting experience were ultimate and truly valid, and that by thinking after the fashion of "mathematical atheists" we could understand experience as well as it can be understood. If the flux of ideas had no other key to it than that system of associations and algebraic substitutions which is called the natural world we should indeed know just as well what to expect in practice and should receive the same education in perception and reflection; but what difference would there be between such an idealist and the most pestilential materialist, save his even greater wariness and scepticism? Berkeley at this time—long before days of "Siris" and tar-water—was too ignorant and hasty to understand how inane all spiritual or poetic ideals would be did they not express man's tragic dependence on nature and his congruous development in her bosom. He lived in an age when the study and dominion of external things no longer served directly spiritual uses. The middle-men had appeared, those spirits in whom the pursuit of the true and the practical never leads to possession of the good, but loses itself, like a river in sand, amid irrational habits and passions. He was accordingly repelled by whatever philosophy was in him, no less than by his religious prejudices, from submergence in external interests, and he could see no better way of vindicating the supremacy of moral goods than to deny the reality of matter, the finality of science, and the constructive powers of reason altogether. With honest English empiricism he saw that science had nothing absolute or sacrosanct about it, and rightly placed the value of theory in its humane uses; but the complementary truth escaped him altogether that only the free and contemplative expression of reason, of which science is a chief part, can render anything else humane, useful, or practical. He was accordingly a party man in philosophy, where partisanship is treason, and opposed the work of reason in the theoretical field, hoping thus to advance it in the moral.
Puerility in morals.
Of the moral field he had, it need hardly be added, a quite childish and perfunctory conception. There the prayer-book and the catechism could solve every problem. He lacked the feeling, possessed by all large and mature minds, that there would be no intelligibility or value in things divine were they not interpretations and sublimations of things natural. To master the real world was an ancient and not too promising ambition: it suited his youthful radicalism better to exorcise or to cajole it. He sought to refresh the world with a water-spout of idealism, as if to change the names of things could change their values. Away with all arid investigation, away with the cold algebra of sense and reason, and let us have instead a direct conversation with heaven, an unclouded vision of the purposes and goodness of God; as if there were any other way of understanding the sources of human happiness than to study the ways of nature and man.
Converse with God has been the life of many a wiser and sadder philosopher than Berkeley; but they, like Plato, for instance, or Spinoza, have made experience the subject as well as the language of that intercourse, and have thus given the divine revelation some degree of pertinence and articulation. Berkeley in his positive doctrine was satisfied with the vaguest generalities; he made no effort to find out how the consciousness that God is the direct author of our incidental perceptions is to help us to deal with them; what other insights and principles are to be substituted for those that disclose the economy of nature; how the moral difficulties incident to an absolute providentialism are to be met, or how the existence and influence of fellow-minds is to be defended. So that to a piety inspired by conventional theology and a psychology that refused to pass, except grudgingly and unintelligently, beyond the sensuous stratum, Berkeley had nothing to add by way of philosophy. An insignificant repetition of the truism that ideas are all "in the mind" constituted his total wisdom. To be was to be perceived. That was the great maxim by virtue of which we were asked, if not to refrain from conceiving nature at all, which was perhaps impossible at so late a stage in human development, at least to refrain from regarding our necessary thoughts on nature as true or rational. Intelligence was but a false method of imagination by which God trained us in action and thought; for it was apparently impossible to endow us with a true method that would serve that end. And what shall we think of the critical acumen or practical wisdom of a philosopher who dreamed of some other criterion of truth than necessary implication in thought and action?
Truism and sophism.
In the melodramatic fashion so common in what is called philosophy we may delight ourselves with such flashes of lightning as this: esse est percipi. The truth of this paradox lies in the fact that through perception alone can we get at being—a modest and familiar notion which makes, as Plato's "Theætetus" shows, not a bad point of departure for a serious theory of knowledge. The sophistical intent of it, however, is to deny our right to make a distinction which in fact we do make and which the speaker himself is making as he utters the phrase; for he would not be so proud of himself if he thought he was thundering a tautology. If a thing were never perceived, or inferred from perception, we should indeed never know that it existed; but once perceived or inferred it may be more conducive to comprehension and practical competence to regard it as existing independently of our perception; and our ability to make this supposition is registered in the difference between the two words to be and to be perceived—words which are by no means synonymous but designate two very different relations of things in thought. Such idealism at one fell swoop, through a collapse of assertive intellect and a withdrawal of reason into self-consciousness, has the puzzling character of any clever pun, that suspends the fancy between two incompatible but irresistible meanings. The art of such sophistry is to choose for an axiom some ambiguous phrase which taken in one sense is a truism and taken in another is an absurdity; and then, by showing the truth of that truism, to give out that the absurdity has also been proved. It is a truism to say that I am the only seat or locus of my ideas, and that whatever I know is known by me; it is an absurdity to say that I am the only object of my thought and perception.
Reality is the practical made intelligible.
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