there as quickly as possible. A stone thrown up in the air tends to return as fast as possible to its position as close as it can get to the center of the earth, just as a mouse that has been driven from its hole tries to return there as soon as possible when the animal from which it fled is gone.
It is of course possible that the stone will be prevented from falling. This occurs when a “violent” force acts on it. According to the ancient philosophers: “A physician seeks to cure, but obstacles can prevent him from achieving his aim.” This analogy presents the organismic point of view in probably the crudest form.
There are also motions that apparently serve no purpose. Theydo not tend toward any goal, but simply repeat themselves. Such are the movements of the celestial bodies, and they were therefore regarded as spiritual beings of a much higher nature. Just as it was the nature of the lower organism to strive toward a goal and flee from danger, so it was the nature of the spiritual bodies to carry out eternally identical movements.
This organismic conception had its basis in teachings of the Greek philosopher Aristotle. Although it was basically a heathen philosophy, it is to be found throughout the entire medieval period with only slight modifications in the doctrine of the leading Catholic philosopher, Thomas Aquinas, as well as in the teachings of the Jewish philosopher Moses Maimonides, and the Mohammedan Averroës.
3.
Mechanistic Physics and Philosophy
The transition from organismic to mechanistic physics is most clearly and in a certain sense most dramatically embodied in the person of Galileo Galilei. He looked upon the Copernican theory of the earth’s motion as something more than just an “astronomical” hypothesis for the simple representation of observations which says nothing about reality. He dared to throw doubt on the very basic principle of medieval physics.
Galileo took as his starting-point the motion of an object along a straight line with constant velocity. This is a type of motion that is most easily represented by a mathematical treatment. He then considered the motion along a straight line with constant acceleration; that is, when the velocity increases by a constant amount during each unit of time. Galileo tried to understand more complex types of motion on the basis of these simple forms. In particular he discovered as a characteristic property of all falling bodies and flying projectiles that their downward acceleration was constant. He was thus able to consider their entire motion as being made up of two components:
(1) a motion where the initial velocity remains constant both in direction and in magnitude (inertial motion); and
(2) a motion with constant acceleration directed vertically downward (action of gravity).
Sir Isaac Newton later extended this scheme to the more complicated motion of the celestial bodies and then to all motion ingeneral. For the circular motion of the planets, such as the earth, around the sun, Newton decomposed the motion into:
(1) the inertial motion, where the initial velocity remains constant both in direction and in magnitude; and
(2) the action of the gravitational force between the sun and the earth whereby the earth receives an acceleration that is directed toward the sun and is inversely proportional to the square of the distance between the earth and the sun.
He then developed these ideas into his celebrated laws of motion and the theory of gravitation:
Law 1:
Every body continues in its state of rest or of uniform motion in a straight line unless it is compelled to change that state by forces impressed upon it (Law of Inertia);
Law 2:
The change of motion is proportional to the force impressed, and takes place in the direction in which the force is impressed (Law of Force);
Law 3:
To every action there is always opposed an equal reaction; and
The Universal Law of Gravitation:
Every particle of matter in the universe attracts every
It is of course possible that the stone will be prevented from falling. This occurs when a “violent” force acts on it. According to the ancient philosophers: “A physician seeks to cure, but obstacles can prevent him from achieving his aim.” This analogy presents the organismic point of view in probably the crudest form.
There are also motions that apparently serve no purpose. Theydo not tend toward any goal, but simply repeat themselves. Such are the movements of the celestial bodies, and they were therefore regarded as spiritual beings of a much higher nature. Just as it was the nature of the lower organism to strive toward a goal and flee from danger, so it was the nature of the spiritual bodies to carry out eternally identical movements.
This organismic conception had its basis in teachings of the Greek philosopher Aristotle. Although it was basically a heathen philosophy, it is to be found throughout the entire medieval period with only slight modifications in the doctrine of the leading Catholic philosopher, Thomas Aquinas, as well as in the teachings of the Jewish philosopher Moses Maimonides, and the Mohammedan Averroës.
3.
Mechanistic Physics and Philosophy
The transition from organismic to mechanistic physics is most clearly and in a certain sense most dramatically embodied in the person of Galileo Galilei. He looked upon the Copernican theory of the earth’s motion as something more than just an “astronomical” hypothesis for the simple representation of observations which says nothing about reality. He dared to throw doubt on the very basic principle of medieval physics.
Galileo took as his starting-point the motion of an object along a straight line with constant velocity. This is a type of motion that is most easily represented by a mathematical treatment. He then considered the motion along a straight line with constant acceleration; that is, when the velocity increases by a constant amount during each unit of time. Galileo tried to understand more complex types of motion on the basis of these simple forms. In particular he discovered as a characteristic property of all falling bodies and flying projectiles that their downward acceleration was constant. He was thus able to consider their entire motion as being made up of two components:
(1) a motion where the initial velocity remains constant both in direction and in magnitude (inertial motion); and
(2) a motion with constant acceleration directed vertically downward (action of gravity).
Sir Isaac Newton later extended this scheme to the more complicated motion of the celestial bodies and then to all motion ingeneral. For the circular motion of the planets, such as the earth, around the sun, Newton decomposed the motion into:
(1) the inertial motion, where the initial velocity remains constant both in direction and in magnitude; and
(2) the action of the gravitational force between the sun and the earth whereby the earth receives an acceleration that is directed toward the sun and is inversely proportional to the square of the distance between the earth and the sun.
He then developed these ideas into his celebrated laws of motion and the theory of gravitation:
Law 1:
Every body continues in its state of rest or of uniform motion in a straight line unless it is compelled to change that state by forces impressed upon it (Law of Inertia);
Law 2:
The change of motion is proportional to the force impressed, and takes place in the direction in which the force is impressed (Law of Force);
Law 3:
To every action there is always opposed an equal reaction; and
The Universal Law of Gravitation:
Every particle of matter in the universe attracts every
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