be a vacuum or no: for if they had not the idea of space without body, they could not make a question about its existence; and if their idea of body did not include in it something more than the bare idea of space, they could have no doubt about the plenitude of the world; and it would be as absurd to demand whether there were space without body, as whether there were space without space, or body without body, since these were but different names of the same idea.
Extension being inseparable from body, proves it is not the same.§ 25. It is true, the idea of extension joins itself so inseparably with all visible and most tangible qualities, that it suffers us to see no one, or feel very few external objects, without taking in impressions of extension too. This readiness of extension to make itself be taken notice of so constantly with other ideas has been the occasion, I guess, that some have made the whole essence of body to consist in extension; which is not much to be wondered at, since some have had their minds, by their eyes and touch (the busiest of all our senses), so filled with the idea of extension, and as it were wholly possessed with it, that they allowed no existence to any thing that had not extension. I shall not now argue with those men who take the measure and possibility of all being only from their narrow and gross imaginations; but having here to do only with those who conclude the essence of body to be extension, because they say they cannot imagine any sensible quality of any body without extension, I shall desire them to consider, that had they reflected on their ideas of tastes and smells as much as on those of sight and touch: nay, had they examined their ideas of hunger and thirst, and several other pains, they would have found that they included in them no idea of extension at all; which is but an affection of body, as well as the rest, discoverable by our senses, which are scarce acute enough to look into the pure essences of things.
