A world of atoms and void › What Comes from What?

Book I begins the physical explanation with the principle that nothing comes from nothing. Lucretius appeals to the regular conditions of generation: particular things arise from appropriate sources and under appropriate conditions. If generation required no determinate source, he argues, the familiar restrictions on what grows from what would be inexplicable. The argument connects an unseen underlying account to the patterned world that readers can observe.

He also argues that things do not vanish into absolute nothing. Their dissolution returns material to the processes from which other things form. The death of a compound and the destruction of its underlying constituents must therefore be distinguished. A particular arrangement can cease while the bodies composing it remain available for other arrangements.

This provides a useful first distinction between the whole and its constituents. Imagine taking apart a mosaic and reusing its pieces in another design. The first image has gone even though its pieces remain. The illustration helps explain how material persistence can coexist with the ending of a particular thing. It is a modern teaching example, not evidence for Lucretius's claim that ultimate bodies are indestructible.

His further argument for ultimate bodies cannot rest on directly seeing them. In Book I he points to things whose effects are evident although their material operation escapes sight, including wind and the moisture gained and lost by clothes. The aim is to show that invisibility does not by itself establish nonexistence. That is a reasonable distinction between a limit of observation and the absence of an object. It remains a further question whether the particular unseen entities he proposes are the best explanation.