The Collected Works of Benedict de Spinoza

But this entire unity of the subject with the object is not necessarily such, except when the subject is thinking. Furthermore, every deduction of derived or special reasons from one absolute and inherently true principle does not occur except in the realm, so to speak, of reason or formal truth. Finally, that necessary identification of different things, without which there would be neither affirmation nor negation, likewise pertains to the form of thinking. But whether two objects, which are in the mind and which are now taken for one by the thinker in a certain respect—that is, are conceived under the form of unity—are one through their own nature (which we are forced to attribute to those things we cannot help but think of with the notion of existence), or whether they merely seem to be one to the thinker at this moment, that thinker, however much he is a subject-object (that is, thinks from his subjective unity with the object), cannot formally judge and decide. Everyone shouts or senses that this depends on the matter; but matter (I mean the internal matter of thinking) does not depend on the mode by which it is now thought by this or that person, that is, reduced from diversity to unity. Rather, the ideal object—that is, that which is in the mind and because of which the mind can rightly be called a subject-object—is subject to the necessity or reality of its own nature whenever it presents itself to the mind to be thought of along with existence, such that the ideal object cannot be formally identified with another in vain or erroneously, unless it is necessarily and