Definitions and Kinds of Motion

Growth and nutrition are common to both plants and animals.

• These are effects of Nature, not the soul

But feeling and voluntary motion are peculiar to animals.

• These are effects of the soul

Some people think that plants have a soul as well.

This leads to 2 kinds of soul:

1. Vegetative
2. Sensory

This is strange.

I think, with most people, that:

• animals are governed by their soul and by their nature.
• plants are governed by their nature alone

Chapter 2: Definition of Terms

Rest is a body not undergoing any change from its existing state.

Motion is a body departing from the state of rest.

Qualitative motion is a change in qualities.

• A motion in respect to colour is when the white body becomes black.
• A motion in respect to flavor is when a sweet thing becomes bitter.
• A motion in respect to temperature is when a warm thing becomes cold.

All these have change. And so change is one kind of motion.

A change in position, such as passing from one place to another, is called transference.

Kinds of Motion

1. Simple

2. Primary

while compounded from them we have growth and decay,11 as when a small thing becomes bigger, or a big thing smaller, each retaining at the same time its particular form.

1. Genesis

This is a coming into existence

2. Destruction

This is the opposite.

The Sophists, however, while allowing that bread in turning into blood becomes changed as regards sight, taste, and touch, will not agree that this change occurs in reality.

Some of them believe that all such phenomena are tricks and illusions of our senses.

the senses, they say, are affected now in one way, now in another, whereas the underlying substance does not admit of any of these changes to which the names are given.

Others (such as Anaxagoras) believe that:

• the qualities do exist in it
• but that they are unchangeable and immutable from eternity to eternity
• these apparent alterations are brought about by separation and combination.

They are refuted by:

• Aristotle’s “On Complete Alteration of Substance”
• the work by Chrysippus.

These opinions were shared by Hippocrates, who lived much earlier than Aristotle.

Hippocrates was the first to:

• demonstrate that:
  • there are 4 mutually interacting qualities
  • to the operation of these is due the genesis and destruction of all things that come into and pass out of being.
• recognise that all these qualities have intimate mingling with one another

The writings of Hippocrates has the beginnings of the proofs which Aristotle later wrote about.

Zeno of Citium afterwards declared that the substances and their qualities undergo this intimate mingling.

In this way, nobody will suppose that bread represents a kind of meeting-place for bone, flesh, nerve, and all the other parts, and that each of these subsequently becomes separated in the body and goes to join its own kind;

before any separation takes place, the whole of the bread obviously becomes blood; (at any rate, if a man takes no other food for a prolonged period, he will have blood enclosed in his veins all the same).

This disproves the view of those who consider the elements unchangeable, as also, for that matter, does the oil which is entirely used up in the flame of the lamp, or the faggots which, in a somewhat longer time, turn into fire.

How many is the number and character of the faculties of Nature?

What is the effect which each naturally produces?

Now, of course, I mean by an effect22 that which has already come into existence and has been completed by the activity of these faculties—for example, blood, flesh, or nerve.

‘Activity’ is the active change or motion.

‘Faculty’ is the cause of this activity.

Thus, when food turns into blood, the motion of the food is passive, and that of the vein active.

Similarly, when the limbs have their position altered, it is the muscle which produces, and the bones which undergo the motion.

In these cases I call the motion of the vein and of the muscle an activity, and that of the food and the bones a symptom or affection,24 since the first group undergoes alteration and the second group is merely transported.

Some might say that “activity” is an effect of Nature.

For example, digestion, absorption, blood-production.

But not in every case is the effect an activity.

Thus, flesh is an effect of Nature.

But it is not an activity.