  Epicurus had attached enormous importance to the internal structure of atoms, which he held to consist of altogether partless magnitudes called ‘minima’. Lucretius condenses and largely edits out this doctrine. What little he does say in support of it is mixed in with his defence of atoms themselves (1.599–634), rather than exhibited as a separate part of the physical theory. Whether this policy reflects the theory’s difficulty for himself or his readers, the economies entailed by keeping the overall subject matter within the chosen six-book structure, or a theoretical difference from early Epicureanism, is destined to be a matter for speculation only.