A vast leap of the mind is needed to take us from anima and duh, to hard atoms. One of the very early thinkers to negotiate that leap was fifth century BC philosopher Leucippus. He began promoting the idea that all matter is made of atoms in around 430 BC. His student Democritus, strongly advanced the idea. And, soon the philosopher Epicurius was promoting it -- overshadowed though he may have been by Aristotle's acceptance of the concept that matter is built from essences -- of Earth, Air, Fire, and Water.
Then, in the mid-first-century BC, Roman Epicurean philosopher Lucretius revived the idea in a powerful book-length poem that expressed surprisingly accurate ideas about the nature of matter. Lucretius left few tracks. Our best knowledge of him is that one long poem, De Rerum Natura -- On the Nature of Things. It expresses the epicurean simplicity and lucidity of Lucretius's remarkable mind. He scorned the mystery-laden polytheism of Rome. Epicureans believed that things are what they seem to be -- that our senses do not deceive us.
He watched matter dividing, subdividing, and rejoining, and he concluded that matter must be made of tiny building blocks -- of atoms, that divide and rejoin. Although he failed to displace the well-established Aristotelian essences, which were on their way to dominating Western thinking, his work survived because he was such a fine poet.
Latin was a practical and direct language, but Lucretius reshaped it and created beauty as he did. Listen, as he paints a completely modern picture of atoms moving in solids and gases. He writes:
... harried by tireless motion this way, that way, Some crash head-on and rebound over vast chasms, While some veer slightly apart from a close-dealt blow, And atoms that jar and rebound over tiny spaces, So tightly wedged in their assembly, tangled Up in their snagged shapes, intertwined and locked, These constitute the strong rock roots, the rugged Structure of iron and all things of like strength. But the rest, the few that wander the great void, Ricochet far and round from afar vast chasms In speedy return; these atoms furnish for us The thin air and the sunlight in all splendor.
Lucretius leaves us with intimations of atomic bonding, a full kinetic theory of gases, even the motion of photons. And, when nineteenth-century thermodynamicists talked about large sets of atoms, they called them "assemblies." That was pure Lucretius, for he had used the Latin word for the Greek citizens' assembly when he talked about aggregate atomic behavior.
De Rerum Natura was still standard classic literature when Aristotle's science began crumbling in the 1600s. The poem was such a rich trove of ideas -- ideas out of place in time, modern ideas of heat, Galilean ideas about falling, ideas that would've been bypassed and forgotten, had they not been so beautifully said. The ideas expressed in de Rerum Natura survived as poetry. As science, they fell by the wayside for the next sixteen centuries.
Platonist philosophy, which embraced Aristotelian science, became ascendant. Until we had a far more mechanical conception of science, atomism could not prevail over the idea that matter was alchemical essence. Atomism would have to wait for the seventeenth-century scientific revolution. Until we began working out the mechanics of particle interactions, gases would remain ephemeral. And, only after we once again were ready to grant that air and steam had corporeal substance, would we finally create steam-powered engines.
For a short account of Lucretius life see the article on Lucretius in the Dictionary of Scientific Biography, Vol. VIII (C.C. Gilespie, ed.) (New York: Charles Scribner's Sons, 1973), or see Lucretius, On the Nature of Things: De Rerum Natura. (Anthony M. Esolen, ed. and transl.) (Baltimore: The Johns Hopkins University Press, 1995).