materials necessary for it. The Ego of the Newton who invents the differential calculus is the same Ego who had learned the numeration table. Without the metaphysical unity of the Me, there could be no synthetical unity of thought, and without the synthetical unity of thought, there could be no science for man.1

Galluppi, Elementi di Filosofia, vol. iii. c. iii. §§ xxiv.-xxv.

CHAPTER II.

ORIGIN OF OUR IDEA OF CORPOREAL SUBSTANCE.

ARTICLE I.

A way to demonstrate the existence of bodies.

672. Having now shown that the sentient subject (the spirit, the Ego) cannot be that which we mean by the term body; let us examine whether what is meant by this term really exists, or is a mere figment of the imagination. This is the same as to inquire whether the corporeal substance exists, as attested by the general sense of mankind, and whence our idea of it is derived.

If I can explain how we form the idea of body, and how it is, that in forming this idea we become reasonably persuaded that bodies really exist, the existence of the bodies themselves will also have been demonstrated.

But the whole force of this demonstration, drawn from the origin of our persuasion of the existence of bodies, depends on the supposition that reasoning, of which the intellectual perception is the first link, is valid for finding as well as proving the truth.

The generality of men admit this as the most certain of all things; but there has now sprung up a school of Sceptics who attempt to call it in question.

With regard to these, I shall, in the next Section, be obliged to solve the objections that are preferred against the validity of reasoning; and that will set the seal on the demonstration which I am giving here of the real existence of bodies.

673. I have said, that the word body is that of 'A proximate cause of our sensations,' and 'A subject of the sensible qualities' (667).

I am therefore bound to show how we acquire a reasonable persuasion that 'A cause of our sensations external to ourselves' exists, and that 'This cause is the subject of the sensible qualities.' '

1

This can be very easily done by recalling to mind what has been said before.

ARTICLE II,

There exists a proximate cause of our sensations.

674. Our sensations suppose a cause distinct from ourselves.

Our external sensations are facts in respect of which we are passive (662–666).

Passive facts are actions which take place in us, but of which we are not the cause (Ibid.)

But, by the principle of causation (567–569), the actions which take place in us, but of which we are not the cause, suppose a cause distinct from ourselves.

Therefore our sensations suppose a cause distinct from ourselves; which was the thing to be demonstrated.

ARTICLE III.

The cause distinct from ourselves is a substance.

675. Our sensations, then, suppose a cause distinct from ourselves (674).

But we have seen that a cause is always a substance (620, &c.)

Therefore the cause of our sensations is a substance.

ARTICLE IV.

The substance which causes our sensations, is immediately conjoined

with them.

676. Our sensations are actions which take place in us, but of which we are not the cause (662–666).

1 These definitions are based, as I said before, on the meaning which

common usage attaches to the term body.

To experience in ourselves an action of which we are not the cause, is the same as to experience a force which has the power of producing a modification in us.

This force is a substance which acts and is called body (667).

Therefore the action which we experience from a body, is the effect, not of a particular power of that body, but of the body itself; and this in virtue of the definition. For, body is precisely that which acts on us in such a manner as to produce sensations in us; and we do not recognise any other co-ordinate powers in the agent designated by this word.

Now the action of a substance is always intimately conjoined with that substance, because the force or energy of a being is inseparable from the being itself.

Therefore the substance which causes our sensations is immediately conjoined with them.'

ARTICLE V.

The cause of our sensations is a limited being.

677. The energy or force which produces our sensations, and which we experience in ourselves, is limited; because the action it exercises on us is limited.

Now it is from this very energy or force that we derive the idea of corporeal substance; or, which comes to the same, it is in that energy or force, and nothing else, that we perceive the being distinct from us, and productive of our sensations.

Hence, as that energy whose action we experience in us, is limited; so is the being in which we conceive it; for, to us, this being is nothing but that same energy conceived as existent.

Therefore the being conceived by us as a substance and the proximate cause of our sensations, is limited.

ARTICLE VI.

We give names to things according as our mind conceives them.

678. This proposition is self-evident.

For the better understanding this, see the note under 667.

We can only name the things we know, and in so far as we know them.

ARTICLE VII.

Rule to be observed in the use of words, in order to avoid error.

679. Words, then, express things just as the mind conceives them (678).

Therefore that which is expressed by any given word, is limited by our knowledge.

Consequently, if we attempt to use words in a more extended sense, to make them signify, not simply what our mind conceives in a being, but that also which might be in it, but of which we have neither perception nor knowledge of any sort, we shall be guilty of an abuse of language; and the reasonings founded thereon will be full of ambiguities, sophistical and misleading.

ARTICLE VIII.

Bodies are limited beings.

680. To define body, is the same as to state what that is to which the name of body has been given.

In order, therefore, to define the meaning of this word, we may proceed in two ways, that is, either by analysing all the ideas which enter into that meaning, or by indicating only some one of them, but this so characteristically proper, that we cannot fail, by taking it as our guide, to identify the being which the word designates.

Now for our present purpose, it is sufficient to explain the word body in the second of these ways; later on we shall define it more fully and circumstantially.

We have seen, (1) that our idea of body is formed from the effect which bodies produce in us by their action, namely, from the force or energy we experience in our sensations (640-643);

(2) That, this energy being limited, we can obtain from it the idea of a limited being only (677); and

(3) That therefore all the knowledge we have of body is that of a limited being.