The First Way regarding motion presupposes that “the natural state of things” is rest. Sir Isaac Newton, however, asserts, “motion was as natural a state as rest.” This means that things already at rest tend to continue at rest, and things already in a state of motion tend to continue also in motion. Does this view, if correct, invalidate in a way the argument of Aquinas regarding motion? Why does motion require an explanation any more than rest?

Things are either in motion or at rest. In The Five Ways of St. Thomas Aquinas, he presents the first way which is an argument from motion. For him, motion includes not only the simple movement of a things from one place to another. It also includes any form of movement or change from one state of a thing to another. In other words, a thing in motion may come at rest, and a thing at rest may come into motion. On the other hand, Sir Isaac Newton, in one of his laws of motion, claims that “motion was as natural a state as rest.” This means that things already at rest tend to continue at rest, and things already in a state of motion tend to continue also in motion. This law of motion is often called the law of inertia.

Newton's law of inertia does not invalidate Aquinas' argument from motion. Actually, it even serves as a supplement to Aquinas' argument from motion. Newton's law of inertia tells us that a thing at rest will remain at rest unless acted on by an unbalanced force, and a thing in motion with the same speed and in the same direction unless acted on by an unbalanced force. We have to notice here now the concept of the absence of force. In the absence of force, an object in motion will remain in motion, and an object at rest will remain at rest. However, when force is present, an object in motion may eventually be at rest, and an object at rest may eventually be in motion. Thus, Newton's and Aquinas' ideas of motion are connected in one way or another.

As we notice, motion requires more explanation than rest. This observation makes sense. Imagine yourself staring at a rubik's cube. Boring, right? Of course, you'd like to get that rubik's cube and solve it. A thing at rest does not have thrill; there is nothing much that we can get from it. For beings like us whose nature is to be curious, more ideas and information can be gathered from things in motion. We won't get anything out of something stationary simply because nothing happens in it than from something moving because movements entail more.