BOOK TWO.

CHAPTER V.

On local motion and its definition.

Local motion, which the Philosopher Referring to Aristotle defines in Physics, Book 5, text 1 and following, is the translation from place to place. This motion is the first and most noble of all others, as Aristotle proves in Physics, Book 8, text 10 and following, because it is the cause and foundation of all other motions.

It is twofold: Rectilinear and Circular.

Rectilinear is that which occurs along a straight line; it is an imperfect motion because it has distinct beginning and end points, and it is a transition from potentiality to actuality.

Circular is that which occurs along a circular line; it is the most perfect motion because the beginning and the end are the same within it, and it is a continuous and uniform act.

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A Single Question.

Whether local motion is the act of a movable thing, insofar as it is movable?

The answer is in the affirmative. Local motion, as defined, is the act of a movable thing insofar as it is movable—that is, insofar as it is in potentiality potentiality The capacity or possibility of a thing to become something else. regarding the place to which it is being moved.

Aristotle, Physics 3, text 14.

The reason is that motion is the act of a being in potentiality, while it is in potentiality. Since, therefore, the movable thing is in potentiality regarding a place, local motion is the act by which the movable thing transitions from potentiality to actuality—namely, to the place in which it ought to rest.