Problems Raised by those who Deny the Existence of Motion...

Problems Raised by those who Deny the Existence of Motion and their Solution Those who have denied the existence of motion in the external world and who have considered it to be a mental concept which refers to a succession of rests have resorted to dubious notions the most important of which are the following two: If motion exists as a single continuous thing in the external world, it must be considered as having parts, and since each of its parts possesses extension, each of these in turn will be divisible into other parts, and this division will continue infinitely.

This implies that finite motion must be infinite. Aristotle responded to this difficulty by claiming that motion does not have actual parts which could be finite or infinite, but rather that it can be divided into two parts, for example, in which case there will be two motions, not a single motion. Likewise, each part may be divided into two or more parts, and with each division performed in the external world a number of actual existents will come about.

These divisions may be continued without end, and hence the supposed motion itself will be finite, although its potential parts will be infinite. No contradiction exists between these two propositions, because one of the conditions for a contradiction is the unity of the actual and the potential which does not obtain in this case, for being finite is the attribute of the motion as a whole, while being infinite is the attribute of its potential parts.

But it is better to ask one who reasons in this way what do you mean by finite motion being infinite? If what is meant by being infinite is the number of its parts, this number does not actually exist in any motion, and the appearance of any number, whether finite or infinite, in motion is due to its objective division, in which case a single motion will not exist.

Likewise, everything which is divisible into two halves is presently a unit, but whenever it is divided, it becomes two units, but this divisibility does not imply that it is both one and two!