The tendency to identify, and the tendency to distinguish, alternate both in scientific thought and in general culture. But whichever prevail for the moment, it is only as a re-action and a protest against the one-sided predominance of the other. And thus both ultimately rest upon and presuppose a ground of existence which is neither mere sameness nor mere difference. It is only when the two tendencies meet and interpenetrate that science accomplishes its end, and discovers the ground of existence. In the first instance the world presents to incipient science the aspect of mere identity and of mere difference. Likeness is confounded with sameness, and unlikeness with diversity. The popular and the infant minds do not draw fine distinctions. Things to them are either the same or different: one point of sameness may in certain conditions obliterate whole breadths of difference; and tiny divergence may make as nothing all the many points of agreement, purely and simply, i. e. abstractly. But the process of comparison, setting things beside each other, teaches us to refine a little, and speak of things as Like or Unlike. One thing is like another when the element of identity preponderates: it is unlike, when the difference is uppermost. Thus while we distinguish things from one another, we connect them. From mere variety, and mere sameness, we have risen, secondly, to distinctions of like and unlike. But, thirdly, this distinction of same and different is in the thing itself. Everything includes an antithesis or contradiction in it: it is at once positive and negative. One can only be virtuous, so long as one is not utterly virtuous.[2] To be a philosopher, implies that you are not wholly or merely a philosopher. The rational animal is so, because of an inherent irrationality, and is so, only as rising upon and superseding it. Every epithet, so to speak, by which you describe any reality, presupposes in it the negative of the quality. Not only does every negation presuppose an attempted or surmised affirmation, but an affirmation is always, it may be said, a re-affirmation against an incipient doubt. Every stage of reality involves the presence of antithetical but inseparable elements: every light implies a shadow to set it forth. The epithet of each real is only _a potiori._ While it retains itself, it must lose itself. Its positivity is only secured by its self-negation and its identity is based upon its self-distinction. Every proposition which conveys real knowledge is a statement that self-sameness is combined with difference. Every such proposition is synthetical: it unites or identifies what is supposed to be implicitly different, or differentiates what seemed only identical. Here we have that _coincidentia oppositorum,_ which is the truth of essence. Thus, e. g. the essence of the Self is the contradiction between its self-centred unity and its existence by self-differentiation into elements.