Question

Subject philosophy:- Describe Aristotle's theory of the cosmos and his understanding of physical motion.

Answer 1

Ans) The first main component to Aristotle’s discussion is the nature of the universe. Aristotle concluded that three things make up a physically constituted entity: bodies and magnitudes, beings possessed of body and magnitude, and the principles of causes of these beings. Magnitude divided in one direction is a line, in two directions is a surface, and in three directions, a body. His view was much like our understanding today. We know a line (length) is one dimensional, a shape is two-dimensional (length & width), and most objects in our everyday life, including us, are three-dimensional (length, width, depth). This concept is over 2,000 years old.

- Aristotle took it one step further with his observations of motion. Aristotle postulated that all bodies have a natural way of moving, which could be regular or irregular. He believed that everything that moved was moved by something.

- The latter is only possible when the irregularity of the movement proceeds from either the mover or from the object moved or both. Basically, this is saying bodies could naturally move in a straight line or not all.

- This idea is actually a rudimentary form of Newton’s first law of motion (an object will remain at rest or in uniform motion in a straight line unless acted upon). He also introduced a third option which was circular motion.

- Aristotle noted that the motion of the body moving upward would be fire or air, and downward would be water or earth. This would mean the objects that could be effected by circular motion must be of an exalted substance.

- Circular motion is connected with more 'heavenly bodies' such as planets. The planets that were allowed to be in circular motion were spheres. These planets revolve around an Earth. He believed the initial motion of the objects was from a 'prime body' who acted on the outermost sphere.

- Since these spheres are moving in a circular motion, they could neither have weight or lightness as they cannot move naturally or unnaturally towards or away from the centre. The prime body was seen as always running and eternal, going past any other element. This element was known as aether or quintessence.

- Essentially, this was the fifth element which made up the Sun, planets and stars. Aether or αἰθήρ was described as a pure, perfect substance, which is unlike anything else on Earth.