Among the lost treasures of Hellenic intellect, there are few which are more to be regretted than the works of Demokritus. Little is known of them except the titles: but these are instructive as well as multifarious. The number of different subjects which they embrace is astonishing. Besides his atomic theory, and its application to cosmogony and physics, whereby he is chiefly known, and from whence his title of _physicus_ was derived--we find mention of works on geometry, arithmetic, astronomy, optics, geography or geology, zoology, botany, medicine, music, and poetry, grammar, history, ethics, &c.[244] In such universality he is the predecessor, perhaps the model, of Aristotle. It is not likely that this wide range of subjects should have been handled in a spirit of empty generality, without facts or particulars: for we know that his life was long, his curiosity insatiable, and his personal travel and observation greater than that of any contemporary. We know too that he entered more or less upon the field of dialectics, discussing those questions of evidence which became so rife in the Platonic age. He criticised, and is said to have combated, the doctrine laid down by Protagoras, "Man is the measure of all things". It would have been interesting to know from what point of view he approached it: but we learn only the fact that he criticised it adversely.[245] The numerous treatises of Demokritus, together with the proportion of them which relate to ethical and social subjects, rank him with the philosophers of the Platonic and Aristotelian age. His Summum Bonum, as far as we can make out, appears to have been the maintenance of mental serenity and contentment: in which view he recommended a life of tranquil contemplation, apart from money-making, or ambition, or the exciting pleasures of life.[246] [Footnote 244: See the list of the works of Demokritus in Diogen. Laert. ix. 46, and in Mullach's edition of the Fragments, p. 105-107. Mullach mentions here (note 18) that Demokritus is cited seventy-eight times in the extant works of Aristotle, and sometimes with honourable mention. He is never mentioned by Plato. In the fragment of Philodemus de Musica, Demokritus is called [Greek: a)nê\r ou) phusiologô/tatos mo/non tô=n a)rchai/ôn, a)lla\ kai\ peri\ ta\ i(storou/mena ou)deno\s ê)=tton polupra/gmôn] (Mullach, p. 237). Seneca calls him "Democritus, subtilissimus antiquorum omnium".--Quæstion. Natural. vii. 2. And Dionysius of Hal. (De Comp. Verb. p. 187, R.) characterises Demokritus, Plato, and Aristotle (he arranges them in that order) as first among all the philosophers, in respect of [Greek: su/nthesis tô=n o)noma/tôn].] [Footnote 245: Plutarch, adv. Kolôten, p. 1108. Among the Demokritean treatises, was one entitled Pythagoras, which contained probably a comment on the life and doctrines of that eminent man, written in an admiring spirit. (Diog. Laert. ix. 38.)]