Marsilio Ficino’s Platonic Theology, Volume II

11Individual human beings differ through other things which attach to them from without and do not belong to the species at all. This indicates the species’ simplicity. That simplicity is also strongly indicated by the fact that a species does not admit of more or less, but stands at a certain fixed degree of nature from which nothing can be added or taken away without changing the species itself. The species of numbers bear witness to this. Seven is a certain species of number. Add one and you create a new species, namely eight; subtract one and you have six, again a new species of number. Knowledge, moreover, properly concerns neither individuals nor genera, but species. Individuals, because they are innumerable and subject to change, are neither comprehended nor firmly retained; genera, because of their confusion within themselves, are not perfectly distinguished. Since, I say, knowledge concerns species, and species are simple, the knowledge of them is also simple—if knowledge is the attainment of truth. Truth is the conformity of things with minds. We should not be troubled by the multitude of words or the variety of many thoughts from which knowledge may seem to be composed. These are preparations for knowledge, or its attendants. Knowledge is one act or habit: I mean the simple touch of a simple form, the indivisible beholding of indivisible truth, the sudden light of intelligence.

12Their error is refuted more clearly still by the fact that many branches of knowledge concern things which are unquestionably indivisible. Who can divide unity? Who can divide simplicity and purity? Who can divide being itself as such? Whatever we divide, moreover, we divide into parts prior to the whole. But these simple things are composed of no preceding parts. We resolve a human being into animal and rational; animal into body and a nature capable of sensation; body into substance and quantity; and substance into being and the capacity to subsist. Into what parts being itself may be resolved I do not know, unless perhaps Plotinus and Proclus resolve it into unity and multiplicity. Yet they will not resolve unity itself any further. No one will resolve unity into numbers, a point into magnitudes, the ultimate form of a thing into another form, or prime matter into matter. Finally, no one will refer those simple concepts of our mind which always shine within us concerning the principles of the sciences to concepts better known or prior. Where resolution ceases, division ceases; where division ends, perfect simplicity is possessed.