Abstract

The thesis of this paper is that Thomas Aquinas offers an alternative model of abstraction (the Active Principle Model) that overcomes the standard objections to abstractionism and expands our view of what an abstractionist theory might look like. I contend that this alternative model of abstraction has been invisible in plain sight, in Aquinas’s references to the mind’s abstractive mechanism as an “intellectual light.” Such language is not metaphorical but rather technical, signaling that intellectual abstraction is to be modeled on the activity of physical light as he understood it from theories proposed by Avicenna and Averroes. The Active Principle Model requires us to rethink Aquinas’s account of how we come to know essences—a process that turns out to be much more tentative and incremental than previously thought.