De Piscibus Libri V et De Cetis Liber Unus

And there is indeed a reason why such a reduction of all finite things to an infinite unity should greatly please the intellect or the logical faculty. For the act of thinking consists solely in the thinker perceiving the unity of those things which, in another respect, are diverse, or indeed can be most diverse. A is predicated of B insofar as it is understood that B inheres in A in the sense currently under discussion. From this it is clear, and has long since been shown, that the formal or logical investigation of truth is to be compared with arithmetical permutation, by which two numbers appearing under different forms are nonetheless and remain the same, just as 2 x 3 = 6. It follows spontaneously that there cannot be a higher canon in that very formal investigation of truth than this: that more things should always be reduced to one, from which those who think do not, and cannot, cease to raise individuals to species, species to general classes, and also to refer all derived or applied laws to one principle in thought and to deduce them from thence. Nor is it difficult to understand that everything about which thought is occupied, and which they call the object—not insofar as it exists outside of thought, but insofar as it is present to the mind (whether as something existing or as something merely thinkable), or indeed is now an inherent part of the mind—can be reached and treated by thinking and willing. Whence, if the thinker is called the subject, it becomes clear that he, while thinking, is entirely a subject-object, or that one unity of the subjective and objective.