History of
Ancient Philosophy

Professor Gale Justin

Aim of the Metaphysics:

nTo identify the basic principles of sensible entities.

nTo then explain by means of these principle how it is that sensible entities can change.

With respect to the principles of sensible entities, Aristotle concludes:

There are three basic principles: matter (which varies from kind to kind in different species), and two basic contraries, form and privation (i.e. actual properties and the potentiality for certain other properties).

For Aristotle:

nForms never exist separately from matter.

nMatter never exists without some forms in it.

nSensible entities are matter-form combinations, which undergo change by gaining and losing forms.

Concerning causes, Aristotle enumerates in Physics Book 1 ch. 3:

Four causes or causal factors, not all of which need to be cited in explaining every change.

Aristotle’s Four Causes are:

nForm: “what the being of the thing would be”

nMatter: “that from which a thing comes to be”

nMoving (efficient) cause: “initiator of motion”

nEnd/Goal: “that for the sake of which”

Examples of Four Causes are:

nForm: house plan

nMatter: House materials

nMoving (efficient) cause: House Builder

nEnd/Goal: shelter and protection of persons and things

So one might say:

The house is a two story French colonial because that was the house plan of the architect. It is constructed out of brick and mortar by the builder and because of the need for shelter and protection.

In other words:

This is the way we speak about the causes of the house.

How these causes work:

The efficient cause, such as a builder, introduces into the composite of matter and form, namely, the bricks, another form—the house design—which the bricks have the potential to acquire. So the effect of the builder’s motion is to actualize the form of a house in matter that has the potential for that kind of form.

Aristotle’s explanation of change is better than any Pre-Socratic theory:

nIt is plausible. We do reference these different factors when we explain why a sensible entity has changed.

nHis theory can also explain not only how sensible entities change but also why sensible entities change in regular ways.

Since for Aristotle, all change requires a moving cause, the question arises whether there is some first cause of motion, something that stands to everything else as the moving cause?

The heavens cause:

nAll natural motions: changes in the seasons, in the weather, growth, decay, change of place, etc.

nare themselves moved by what?

The unmoved mover moves the heavens.

Aristotle’s argument for the existence of an unmoved mover proceeds in three parts.

Aristotle’s proof of unmoved mover:

Part 1: eternality of motion

Part 2: existence of eternal substance(s)

Part 3: existence of an eternal unmoved substance that is a mover

Part 1:

nTime is eternal.

nWherever there is time, there is motion.

nTherefore, motion is eternal.

Support for the claim that time is eternal:

If time is not eternal, then time came to be. If time came to be, then there is some time before time came to be. But that is impossible, so time is eternal.

Support for the claim that wherever there is time, there is motion:

Time is the measure of motion. So wherever there is time, there is motion.

So we get the conclusion of Part 1.

Part 2:

1. But all motion is spatial, since motion just is change of place. (implicit)

2. And only circular motion is eternal, i.e. can have no beginning and no end.

3. Thus, it is evident in theory that something moves with an unceasing circular motion and, in fact, this is the heavens.

Part 3: This part of the argument begins with the fact the motion requires a cause of motion and moves to the conclusion that there exists an unmoved mover.

1. If anything moves, then it is moved by something.

2. The heavens move eternally.

3. Thus, there must be a eternal mover of the eternal heavens.

4. But whatever moves the eternal heavens cannot itself move. Otherwise, there would be an infinite number of movers.

5. So there is an unmoved mover. (p. 376)

What kind of a substance must this unmoved mover be?

It cannot be a material substance because any material substance that moves can potentially cease to move. So it must be a non-sensible, unchangeable, eternal substance.

With regard to the nature of the unmoved mover, Aristotle claims (381-82):

The unmoved is thinking immersed in the activity of thinking itself. Since like a god, it is capable of no practical or productive activity, it can only think and, its thinking must be of what is best, namely, its own thinking!

Aristotle also explains how the unmoved mover moves the heavens:

Just as an object of desire moves a person, so the unmoved mover moves the heavens. The heavenly bodies desire to imitate the orderliness of the unmoved mover.