‘A property’, according to the author of De Rerum Natura in 1.451–4, ‘is that which can never be sundered and separated without fatal dissolution, as weight is to stone, heat to fire, liquidity to water, touch to all bodies, intangibility to void’, seiungi seque gregari. As elsewhere Lucretius, that most committed practitioner of word-play, makes his verb mirror the very separation which it describes.