Although, however, we may justly quarrel with such unlooked-for difficulties, the important question, after all, is not of their obscurity but of their truth. Many things in all the sciences are obscure to an unpractised understanding, which are true enough and clear enough to people acquainted with the subjects, and may be fairly laid as foundations of a scientific system, although rudimentary students must be contented to accept them upon faith. Of course it is entirely competent to Spinoza, or to any one, to define the terms which he intends to use just as he pleases, provided it be understood that any conclusions which he derives out of them apply only to the ideas so defined, and not to any supposed object existing which corresponds with them. Euclid defines his triangles and circles, and discovers that to figures so described certain properties previously unknown may be proved to belong; but as in nature there are no such things as triangles and circles exactly answering the definition, his conclusions, as applied to actually existing objects, are either not true at all or only proximately so. Whether it be possible to bridge over the gulf between existing things and the abstract conception of them, as Spinoza attempts to do, we shall presently see. It is a royal road to certainty if it be a practicable one, but we cannot say that we ever met any one who could say honestly Spinoza had convinced him; and power of demonstration, like all other powers, can be judged only by its effects. Does it prove? does it produce conviction? If not, it is nothing. We need not detain our readers among these abstractions. The real power of Spinozism does not lie so remote from ordinary appreciation, or we should long ago have heard the last of it. Like all other systems which have attracted followers, it addresses itself not to the logical intellect but to the imagination, which it affects to set aside. We refuse to submit to the demonstrations by which it thrusts itself upon our reception, but regarding it as a whole, as an attempt to explain the nature of the world, of which we are a part, we can still ask ourselves how far the attempt is successful. Some account of these things we know that there must be, and the curiosity which asks the question regards itself, of course, as competent in some degree to judge of the answer to it. Before proceeding, however, to regard this philosophy in the aspect in which it is really powerful, we must clear our way through the fallacy of the method.