and the same sense, therefore belong to the same subject or substrate; where the principle (_i.e._ the source, or faculty) of the _knowledge_ of two objects is the same, the principle (_i.e._ elementary form) of their _existence_ is also one. (Examples are the curved and the plane, the concave and the convex, anger and patience, pride and humility, miserliness and liberality). In conclusion:--"He who would know the greatest secrets of nature, let him regard and contemplate the minima and maxima of contraries and opposites. _Profound magic it is to know how to extract the contrary after having found the point of union._" Aristotle was striving towards it, but did not attain it, said Bruno; "remaining with his foot in the _genus_ of opposition, he was so fettered that he could not descend to the _species_ of contrariety ... but wandered further from the goal at every step, as when he said that contraries could not co-exist at the same time in the same subject."[287] There is a naïve but at the same time a bold realism in this demand of Bruno's that reality shall correspond even to the simpler unities of thought--unities which after all are mere limitations. It is only because we cannot distinguish in imagination between an infinite circle and a straight line that their identity in actual existence is postulated, and so the minimal chord and minimal arc coincide to our limited imagination only. Admittedly in the case of sense-qualities the argument is from oneness of faculty knowing to oneness of things known. These, however, are only, as we have said, "signs" and "verifications" of a metaphysical truth which is arrived at by other methods.