On Physics

Now we must consider the division of motion. Motion is divided in one way as follows. Of motions, one is natural, another is violent, and another is animate original: "animalis"; referring to motion originating from a soul or living being, like walking or breathing..

Natural motion is that whose principle is within, namely nature itself For example, a stone falling toward the earth.. Violent motion is that whose principle is outside, with the subject suffering force original: "inferente vim passio"; meaning the object is being acted upon against its natural inclination, like a stone thrown upward.. Animate motion is that whose principle within is the soul original: "anima".

And this division is taken from what Aristotle says in the seventh book of the Physics: "Whatever is moved is moved either by itself or by another."

And note that natural motion is weak at the beginning and intense at the end The closer an object gets to its "natural place," the faster it moves.. Animate motion, however, is weak at the beginning and at the end, but intense in the middle. Violent motion is intense at the beginning and weak at the end The force is strongest when first applied but fades as it moves further from the source..

Aristotle divides violent motion in the seventh book of the Physics into four species: pushing, pulling, carrying, and turning original: "pulsionem, tractionem, vectionem, et vertiginem".

Of pushing, there are two species: namely impulsion and expulsion. Impulsion is when the mover does not leave the object being moved. Expulsion, however, is when the pusher leaves the object. Pulling occurs when the motion of the puller is faster or more forceful toward itself or toward another, and is not separated from that which is pulled. And to this category are reduced breathing in and breathing out, as well as speculation original: "speculatio"; here used in a physical sense of "drawing in" or observing and radiation, which are similar to pulling.

Carrying occurs when something is moved not by its own power but accidentally original: "secundum accidens"; being moved because it is on or in another moving object, like a passenger on a ship.. And this happens in three types of motion: namely, in pushing, pulling, and turning. Turning is a motion composed of pulling and pushing.

In another way, Aristotle divides motion in the Post-predicaments A section of Aristotle's work on logic known as the "Categories." into six species: namely, generation, corruption decay or destruction, increase, decrease, alteration, and change according to place locomotion. Of this last type, there are six directions: namely forward, backward, upward, downward, to the right, and to the left.

But Aristotle corrects himself in the Physics, saying that generation and corruption are not motions, but mutations instantaneous changes of state rather than a continuous process.. Hence he says in the fifth book of the Physics: "These are indeed mutations, but they are not motions." For motion is from a subject to a subject—that is, from one being to another being. Generation, however, is from non-being to being; and corruption is from being to non-being.

Likewise, motion exists only in a thing that is already existing, stable, and within time. Generation and corruption are not in a stable thing, nor in time, but in an instant. Therefore, generation and corruption are not motions, but mutations. Every motion is a mutation, but the reverse is not true. These species must be discussed more fully in the treatise on the elements.

Likewise, note that some things move through space and time, such as bodies. Some move through space but not through time, according to some: for instance, light moving from the east to the west in an instant. Others say that such motion occurs in imperceptible time. Some move through time but not through space, such as an angel In Scholastic thought, angels, being immaterial, could change their "state" over time without occupying physical space.. Something moves neither through time nor through space, such as