Even Aristotle complains of the difficulty of understanding Herakleitus, and even of determining the proper punctuation (Rhetoric. iii. 5).] [Footnote 80: Cicero, Nat. Deor., iii. 14, 35.] [Side-note: Doctrine of Herakleitus--perpetual process of generation and destruction--everything flows, nothing stands--transition of the elements into each other, backwards and forwards.] The expositors followed by Lucretius and Cicero conceived Herakleitus as having proclaimed Fire to be the universal and all-pervading element of nature;[81] as Thales had recognised water, and Anaximenes air. This interpretation was countenanced by some striking passages of Herakleitus: but when we put together all that remains from him, it appears that his main doctrine was not physical, but metaphysical or ontological: that the want of adequate general terms induced him to clothe it in a multitude of symbolical illustrations, among which fire was only one, though the most prominent and most significant.[82] Xenophanes and the Eleates had recognised, as the only objective reality, One extended Substance or absolute Ens, perpetual, infinite, indeterminate, incapable of change or modification. They denied the objective reality of motion, change, generation, and destruction--considering all these to be purely relative and phenomenal. Herakleitus on the contrary denied everything in the nature of a permanent and perpetual substratum: he laid down nothing as permanent and perpetual except the process of change--the alternate sequence of generation and destruction, without beginning or end--generation and destruction being in fact coincident or identical, two sides of the same process, since the generation of one particular state was the destruction of its antecedent contrary. All reality consisted in the succession and transition, the coming and going, of these finite and particular states: what he conceived as the infinite and universal, was the continuous process of transition from one finite state to the next--the perpetual work of destruction and generation combined, which terminated one finite state in order to make room for a new and contrary state. [Footnote 81: To some it appeared that Herakleitus hardly distinguished Fire from Air. Aristotel. De Animâ, i. 2; Sext. Empiric. adv. Mathemat. vii. 127-129, ix. 360.] [Footnote 82: Zeller's account of the philosophy of Herakleitus in the second edition of his Philosophie der Griechen, vol. i. p. 450-496, is instructive. Marbach also is useful (Gesch. der Phil. s. 46-49); and his (Hegelian) exposition of Herakleitus is further developed by Ferdinand Lassalle (Die Philosophie Herakleitos des Dunklen, published 1858). This last work is very copious and elaborate, throwing great light upon a subject essentially obscure and difficult.] [Side-note: Variety of metaphors employed by Herakleitus, signifying the same general doctrine.]