discusses motion () in his Physics quite differently from modern science. Aristotle's definition of motion is closely connected to his actuality-potentiality distinction. Taken literally, Aristotle defines motion as the actuality () of a "potentiality as such". What Aristotle meant however is the subject of several different interpretations. A major difficulty comes from the fact that the terms actuality and potentiality, linked in this definition, are normally understood within Aristotle as opposed to each other. On the other hand, the "as such" is important and is explained at length by Aristotle, giving examples of "potentiality as such". For example, the motion of building is the of the of the building materials as building materials as opposed to anything else they might become, and this potential in the unbuilt materials is referred to by Aristotle as "the buildable". So the motion of building is the actualization of "the buildable" and not the actualization of a house as such, nor the actualization of any other possibility which the building materials might have had. In an influential 1969 paper, Aryeh Kosman divided up previous attempts to explain Aristotle's definition into two types, criticised them, and then gave his own third interpretation. While this has not become a consensus, it has been described as having become "orthodox". This and similar more recent publications are the basis of the following summary. 1. The "process" interpretation and associate this approach with W.D. Ross. points out that it was also the interpretation of Averroes and Maimonides. This interpretation is, to use the words of Ross that "it is the passage to actuality that is ” as opposed to any potentiality being an actuality. The argument of Ross for this interpretation requires him to assert that Aristotle actually used his own word wrongly, or inconsistently, only within his definition, making it mean "actualization", which is in conflict with Aristotle's normal use of words. According to this explanation also can not account for the "as such" in Aristotle's definition. 2. The "product" interpretation associates this interpretation with St Thomas of Aquinas and explains that by this explanation "the apparent contradiction between potentiality and actuality in Aristotle's definition of motion" is resolved "by arguing that in every motion actuality and potentiality are mixed or blended". Motion is therefore "the actuality of any potentiality insofar as it is still a potentiality". Or in other words: The Thomistic blend of actuality and potentiality