Page:Theory of Mind of Roger Bacon.djvu/10



The Theory of Species or Forms is an attempt to explain the phenomena of qualitative change in the world, and indeed in the whole universe—the Aristotelian universe of the Mediaeval thinker. Our Author sets out from Aristotle’s conception of assimilation, and pretends to make a distinct advance upon that conception. The problem is not, therefore, a problem in Logic, with Species as opposed to Genus for the central concept; but a problem in Natural Philosophy, where Species in the Sense of Form or Image or Likeness is the central theme. In the action of one thing upon another, it is that “immediate or first effect of the Agent” which is propagated in the medium and works the secondary effects; such, for example, is the “virtue” of the sun in the air which acts upon wax and melts it, upon clay and hardens it, upon the sense of touch and produces the feeling of warmth.

Of the many words used to express this idea, Bacon furnishes us with a list. Thus, with reference to the process of physical change, the term Virtue is employed, because the Agent is conceived as putting its “virtue” into the thing acted upon. In Optics the term used is Form; and in particular, the reflections in mirrors are called Unsubstantial Forms. And for perception and conception there are various terms in use, such as Species and Impression and Intention and Phantasm, or Simulacrum, and Affection. Species and Impression are used, following the terminology of Aristotle. Intention serves to indicate its unclearness in contrast with the real thing whose likeness it is. As applied to dreams Phantasm and Simulacrum are used, because the Species is taken for the reality which it resembles. And it is called Affection because the medium and the senses are affected and substantially changed by receiving the Species.