Cursus Philosophicus Thomisticus, Prima Pars Philosophiae Naturalis

At present, we omit many things which are usually disputed concerning the science of philosophy, since they can be made known easily from the resolution given in the prefatory question of our book on logic¹ and in the last question of our book on the Posterior Analytics.² Such omitted points include whether philosophy is necessary for us, whether it is a science, whether practical or speculative, and other like questions which are resolved by similar resolution. For it is established that philosophy is necessary for us for a correct and scientific scrutiny of natural things. That it is indeed a science is established from many demonstrations which will be made in the due course of this science; and that it is also speculative is established both from the end of this science, which is the investigation and knowledge of natural truths, not the making of them, and from the principles by which it proceeds, which show the truth in a resolutive mode, rather than teaching how to manufacture it in a compositive mode.

Wherefore only three things remain to be explained which are proper to this science. First, its formal and material object, whatever it may be. Second, its unity, whether it is of one indivisible species, or whether it is divided into diverse species according to diverse objects (e.g., whether that which treats of the heavens is diverse in species from that which treats of generation or of the soul, or whether all this is of one species). Third, the order of knowing, what is first known by our intellect, which Aristotle treated by way of a preface in this first book.