Chapter VII.(19) On The Relation of the Concrete Knowledge of Perception to Abstract Knowledge.
It has been shown that conceptions derive their material from knowledge of perception, and therefore the entire structure of our world of thought rests upon the world of perception. We must therefore be able to go back from every conception, even if only indirectly through intermediate conceptions, to the perceptions from which it is either itself directly derived or those conceptions are derived of which it is again an abstraction. That is to say, we must be able to support it with perceptions which stand to the abstractions in the relation of examples. These perceptions thus afford the real content of all our thought, and whenever they are wanting we have not had conceptions but mere words in our heads. In this respect our intellect is like a bank, which, if it is to be sound, must have cash in its safe, so as to be able to meet all the notes it has issued, in case of demand; the perceptions are the cash, the conceptions are the notes. In this sense the perceptions might very appropriately be called _primary_, and the conceptions, on the other hand, _secondary_ ideas. Not quite so aptly, the Schoolmen, following the example of Aristotle (_Metaph._, vi. 11, xi. 1), called real things _substantiæ primæ_, and the conceptions _substantiæ secundæ_. Books impart only secondary ideas. Mere conceptions of a thing without perception give only a general knowledge of it. We only have a thorough understanding of things and their relations so far as we are able to represent them to ourselves in pure, distinct perceptions, without the aid of words. To explain words by words, to compare concepts with concepts, in which most philosophising consists, is a trivial shifting about of the concept-spheres in order to see which goes into the other and which does not. At the best we can in this way only arrive at conclusions; but even conclusions give no really new knowledge, but only show us all that lay in the knowledge we already possessed, and what part of it perhaps might be applicable to the particular case. On the other hand, to perceive, to allow the things themselves to speak to us, to apprehend new relations of them, and then to take up and deposit all this in conceptions, in order to possess it with certainty—that gives new knowledge. But, while almost every one is capable of comparing conceptions with conceptions, to compare conceptions with perceptions is a gift of the select few. It is the condition, according to the degree of its perfection, of wit, judgment, ingenuity, genius. The former faculty, on the contrary, results in little more than possibly rational reflections. The inmost kernel of all genuine and actual knowledge is a perception; and every new truth is the profit or gain yielded by a perception. All original thinking takes place in images, and this is why imagination is so necessary an instrument of thought, and minds that lack imagination will never accomplish much, unless it be in mathematics. On the other hand, merely abstract thoughts, which have no kernel of perception, are like cloud-structures, without reality. Even writing and speaking, whether didactic or poetical, has for its final aim to guide the reader to the same concrete knowledge from which the author started; if it has not this aim it is bad. This is why the contemplation and observing of every real thing, as soon as it presents something new to the observer, is more instructive than any reading or hearing. For indeed, if we go to the bottom of the matter, all truth and wisdom, nay, the ultimate secret of things, is contained in each real object, yet certainly only _in concreto_, just as gold lies hidden in the ore; the difficulty is to extract it. From a book, on the contrary, at the best we only receive the truth at second hand, and oftener not at all.