the potential as such is an actuality. "The actuality of the potentiality to be on the other side of the room, as just that potentiality, is neither more nor less than the walking across the room." , in his commentary of Aristotle's Physics book III gives the following results from his understanding of Aristotle's definition of motion: The genus of which motion is a species is being-at-work-staying-itself (), of which the only other species is thinghood. The being-at-work-staying-itself of a potency (), as material, is thinghood. The being-at-work-staying-the-same of a potency as a potency is motion. The importance of actuality in Aristotle's philosophy The actuality-potentiality distinction in Aristotle is a key element linked to everything in his physics and metaphysics. Aristotle describes potentiality and actuality, or potency and action, as one of several distinctions between things that exist or do not exist. In a sense, a thing that exists potentially does not exist; but, the potential does exist. And this type of distinction is expressed for several different types of being within Aristotle's categories of being. For example, from Aristotle's Metaphysics, 1017a: We speak of an entity being a "seeing" thing whether it is currently seeing or just able to see. We speak of someone having understanding, whether they are using that understanding or not. We speak of corn existing in a field even when it is not yet ripe. People sometimes speak of a figure being already present in a rock which could be sculpted to represent that figure. Within the works of Aristotle the terms and , often translated as actuality, differ from what is merely actual because they specifically presuppose that all things have a proper kind of activity or work which, if achieved, would be their proper end. Greek for end in this sense is telos, a component word in (a work that is the proper end of a thing) and also teleology. This is an aspect of Aristotle's theory of four causes and specifically of formal cause (, which Aristotle says is ) and final cause (). In essence this means that Aristotle did not see things as matter in motion only, but also proposed that all things have their own aims or ends. In other words, for Aristotle (unlike modern science), there is a distinction between things with a natural cause in the strongest sense, and things that truly happen by accident. He also