theory was already formed in his mind when he wrote his earlier philosophical works, and even some of his peculiar applications of it had already suggested themselves. It is hardly possible, therefore, to find any very marked development in this regard between the London and the Frankfort periods. There is elaboration and completion rather than development in any definite direction;[388] and, as we have seen, the writing of the larger works, containing the developed system, was projected in London, and even carried out to a certain extent before Bruno left England.[389] In the _Acrotismus_, which occupies a middle place between the two periods, the doctrine is equally in evidence, in reference both to the atoms and to the continuous ether in which they move. "There is a limit to the division of nature--an indivisible something; the division of nature arrives at ultimate minimal parts, unapproachable by human instruments. Of these minimal bodies every sensible body is composed, and such a body, resolved into its minima, can retain no semblance of complexity; for these are the first bodies out of which all others are made, and which are, in the truest sense, the matter of all things that have corporeal existence. Resolved into these parts, stone has no look of stone, flesh of flesh, bone of bone; in their elements, bone, stone, and flesh do not differ, but only when formed out of these, compounded, compacted, and arranged in diverse manners, do flesh, stone, and bone and other things become different one from another."[390] And Bruno describes how, between the heavenly bodies, there is a substance, "ingenerable and incorruptible, the immeasurable air, a kind of spiritual body"--the ether.[391] [Sidenote: Object of _De Minimo_.] [Sidenote: Atomism a metaphysical doctrine.]