To inquire into the composition of a substance, is to consider as _one_, many substances, which have not the less an independent existence, because they are in immediate proximity to each other. What we term a _body_, however minute, is a multitude of bodies, or to speak more exactly, an infinite number of bodies, which appear limited to us, indeed, but may perhaps appear, in their true character of infinity, to beings of a higher order, who may be able to distinguish as _infinite_, what our limited senses allow us to perceive only as _finite_. They are _one_, not in nature, but in our thought; as one thousand individuals, that in nature must always be one thousand, receive a sort of unity that is relative merely to our conception, when ranked by us as a single regiment, or as many regiments become _one_ by forming together an army. In the energies of external matter, the innumerable separate bodies are thus regarded by us as _one_, when the space which divides them is not measurable by our imperfect vision, and as distinct or separate, when the space can be measured by us. The _unity_ of the aggregate is here no absolute quality of the mass, but is truly relative to the observer's power of distinguishing the component parts; the mass being one or many, as his senses are less or better able to distinguish these. This whole globe of earth, with its oceans, and rivers, and mountains, and woods, and with all the separate multitudes of its animated inhabitants, may seem to some being of another species, only one continuous and uniform mass; as the masses, that seem to us uniform and continuous, may seem a whole world of separate and varied parts, to the insect population that swarms upon its surface. “A single leaf of a tree,” to borrow an obvious illustration from a French writer, “is a little world inhabited by invisible animals, to whose senses it appears of immense extent, who see in it mountains and abysses that are almost immeasurable, and who, from one side of the leaf to the other, hold as little communication with the opposite animalcula, who have their dwellings there, as we do with our Antipodes.”[23]