1. Many definitions of space have been given. The principal one is this: space is the extent which separates two bodies; from which certain sophists have inferred, that, where no body is, there can be no space. Doctors of theology have taken this idea as the base of their belief, that there is necessarily an end to space, alleging that bodies limited to a certain number cannot form an infinite succession, and that where bodies no longer exist is also the end of space. Yet another definition of space is: the place where worlds move, the void where matter acts, etc. Let us leave, in the treatises where they repose, all these definitions, which define nothing.
Space is one of those words which represents a primitive and axiomatic idea, self-evident, to which the diverse definitions which are given serve only to obscure its meaning. We all know what space is; and I desire only to establish its infinity in order that our subsequent studies may find no barrier opposing itself to the investigation of our ideas.
Now, I say that space is infinite for this reason: that it is impossible to suppose any limit to it, and that, notwithstanding the difficulty of gaining a conception of infinitude, it is, however, easier to think of going eternally through space, than to decide upon a stopping-place in it beyond which no more space extends.
In order to grasp as far as is possible with our limited faculties the infinitude of space, let us suppose ourselves departing from Earth, lost in the midst of infinitude, towards any point in the universe, and that with the exceeding celerity of an electric spark, which traverses thousands of leagues in a second. Scarcely have we left our globe, having passed over millions of miles, we find ourselves in a place whence our Earth will appear to us only under the aspect of a pale star. An instant after, following always the same direction, we shall arrive near the far-distant stars, which you can scarcely distinguish from your terrestrial station; and whence not only the Earth is lost to our sight in the heavenly depths, but also your sun’s splendor is eclipsed by the distance which separates us from it. Propelled incessantly at the same lightning speed, we pass over planetary systems at every step as we advance in space, over islands of ethereal light, over starry ways, and glorious places where God has scattered worlds profusely, as he has sown plants on terrestrial prairies.
Now it is only a few minutes since we took our departure from Earth, and already hundreds of millions of millions of miles separate us from Earth, thousands of worlds have been displayed to our sight, and yet listen! We have in reality advanced but one step in the universe.
If we continue for years, ages, thousands of centuries, hundreds of millions of earthly periods of time, to transverse incessantly with the same lightning speed the fields of space, on whatever side we may go, toward whatsoever point we may direct ourselves from this invisible grain which we have quitted, and which is called Earth, the same immensity of space will be ever before us. This is space.