clxxxii ANALYSIS: MULTIPLICATION OF SPECIES.
VOL. II. PAGES
thing, but a continuous succession, each generating that which follows. It has been said that light is body, or an emanation from body. But Aristotle denies this, remarking that in that case we should perceive its translation from east to west at sunrise. The remarks on the subject in the Topics are not to be taken as conveying Aristotle's real opinion
501-507
CHAPTER 11.
The second question is whether the species of a corporeal agent should be regarded as corporeal or spiritual. Clearly the former: since it is not a soul, or an intelligence, or a first cause; and these only can be considered as spiritual. The species must be of like nature with the agent, and of like nature with the completed effect. It cannot be of nobler nature than that which generates it. Some hold that, though in its essence corporeal, yet its mode of existence is spiritual. But there cannot be this disparateness between the essence and the mode of existence. The essence of the species has dimension, derived as we have seen from the medium; it is therefore corporeal. It is said that it has not material essence (material being here taken for corporeal). But even spiritual substances have material essence: they are compounded of form and of matter: much more, there- fore, are species material. It has been already shown that the species of corporeal substance resembles the total compound. In the medium not merely is the formal essence generated but the material, although the essence be incomplete. I therefore conclude that the species of a corporeal object is corporeal.....507-509
The contrary view has arisen from imperfect translations of Aver- roes, Avicenna, and Aristotle. In these the word insensible has been mistaken for immaterial. And because spiritual things are insensible, therefore what is insensible has been taken to mean spiritual and immaterial. It is objected that species are not always insensible, as when a ray passes through a window or through coloured glass. But this is only accidental. Some expressions of Avicenna as to the reception of impressions in the brain have been wrongly interpreted. They must be taken in connexion with what Aristotle has said on the same subject...509-511
CHAPTER III.
I pass to the question of the mingling of species in the medium. The question is one of much difficulty, but Ptolemy and Alhazen throw great light upon it. Species of the same kind melt into one, and if opposite, then the stronger overwhelms the weaker. Those that are contingent, i.e. have no relation to each other, co-exist
