Aristotle distinguished between natural motion and violent motion. Natural motion is self-caused and persistent, while violent motion is externally caused and transient.
Natural motions include the motions of the heavenly bodies and the elements of earth, water, air, and fire. Violent motions include those caused by humans or animals as well as those caused by natural forces like wind or lightning.
Actually, Aristotle’s distinction between natural and violent motion is important because it helps us understand how objects move in the universe. The distinction allows us to classify all motion into one of two categories: natural or violent.
In Physics, Aristotle states that “natural” motion “is that which tends to persist in its being.” This can be rephrased as “substances tend towards their own being.” For example, a rock naturally falls because it wants to return to its natural state of being at rest on the ground. As another example, fire naturally moves upwards because it wants to return to its natural state of being surrounded by air.
Violent motion is not self-caused, but rather caused by something else (e.g., pushing a rock). It is also transient because once the external cause has stopped acting upon the object, then it no longer moves violently; instead it resumes moving naturally on its own accord (e.g., when you stop pushing a rock, it falls).