Aristotle
Aristotle’s account of motion can be found in the Physics. By motion, Aristotle (384-322 BCE) understands any kind of change. He defines motion as the actuality of a potentiality. Initially, Aristotle’s definition seems to involve a contradiction. However, commentators on the works of Aristotle, such as St. Thomas Aquinas, maintain that this is the only way to define motion.
In order to adequately understand Aristotle’s definition of motion it is necessary to understand what he means by actuality and potentiality. Aristotle uses the words energeia and entelechiainterchangeably to describe a kind of action. A linguistic analysis shows that, by actuality, Aristotle means both energeia, which means being-at-work, and entelechia, which means being-at-an-end. These two words, although they have different meanings, function as synonyms in Aristotle’s scheme. For Aristotle, to be a thing in the world is to be at work, to belong to a particular species, to act for an end and to form material into enduring organized wholes. Actuality, for Aristotle, is therefore close in meaning to what it is to be alive, except it does not carry the implication of mortality.
From the Middle Ages to modern times, commentators disagreed on the interpretation of Aristotle’s account of motion. An accurate rendering of Aristotle’s definition must include apparently inconsistent propositions: (a) that motion is rest, and (b) that a potentiality, which must be, if anything, a privation of actuality, is at the same time that actuality of which it is the lack. St. Thomas Aquinas was prepared to take these propositions seriously. St. Thomas observes that to say that something is in motion is just to say that it is both what it is already and something else that it is not yet. Accordingly, motion is the mode in which the future belongs to the present, it is the present absence of just those particular absent things which are about to be. St. Thomas thus resolves the apparent contradiction between
In order to adequately understand Aristotle’s definition of motion it is necessary to understand what he means by actuality and potentiality. Aristotle uses the words energeia and entelechiainterchangeably to describe a kind of action. A linguistic analysis shows that, by actuality, Aristotle means both energeia, which means being-at-work, and entelechia, which means being-at-an-end. These two words, although they have different meanings, function as synonyms in Aristotle’s scheme. For Aristotle, to be a thing in the world is to be at work, to belong to a particular species, to act for an end and to form material into enduring organized wholes. Actuality, for Aristotle, is therefore close in meaning to what it is to be alive, except it does not carry the implication of mortality.
From the Middle Ages to modern times, commentators disagreed on the interpretation of Aristotle’s account of motion. An accurate rendering of Aristotle’s definition must include apparently inconsistent propositions: (a) that motion is rest, and (b) that a potentiality, which must be, if anything, a privation of actuality, is at the same time that actuality of which it is the lack. St. Thomas Aquinas was prepared to take these propositions seriously. St. Thomas observes that to say that something is in motion is just to say that it is both what it is already and something else that it is not yet. Accordingly, motion is the mode in which the future belongs to the present, it is the present absence of just those particular absent things which are about to be. St. Thomas thus resolves the apparent contradiction between