As Monica Gale notes in the introduction to her edited volume of seminal articles on Lucretius, several studies in the past three decades have confirmed that “Analogy is perhaps the key tool in Lucretius’ argumentative armoury” (Gale 2007: 4). Yet when it comes to the celebrated dust-mote analogy of DRN 2.112-141, the consensus is that the analogy is illustrative, but not probative (Schiesaro 1990: 28–29; Schrijvers 1999: 183–84; Fowler 2002: 187, 190, 192–93, 202). More specifically, the consensus is that (i) the analogy of dust motes (DRN 2.112-124) illustrates the model of atomic collisions. It is also commonly held (Fowler 2002: 187, 193; Bailey 1947: 2:823) that (ii) the illustrative clarity of the analogy provides a πρόληψις (preconception) of atomic motion, on the basis of the phrase vestigia notitiai (DRN 2.124). Further, (iii) Lucretius (in DRN 2.125-141) then infers the existence of atomic collisions by taking the very same phenomenon of dust as the sign of causally underlying atomic motion.
I take issue with each of these three views. I stress that Lucretius treats two distinct phenomena in this passage: the collision of dust motes with each other (DRN 2.112-124) and the erratic motion of individual dust motes (DRN 2.125-141). The consensus tends to conflate the two motions and suppose that the same event both illustrates the theory and is evidence of it. Rather, I hold that the analogy in DRN 2.112-124 is probative of atomic collisions, while 2.125-141 explains the erratic motion of singleton dust particles by reference to the atomic collisions that have just been proven to exist. The advantage of my view is that probative analogy has a rich tradition in both Epicurus and Philodemus, whereas the consensus would attribute to Lucretius an argument that hinges on an inference to the best explanation, a method that can be much less securely attributed to Epicurean methods. Finally, I refute that the dust-mote analogy provides a preconception (πρόληψις) of atomic collisions. It would be controversial for Lucretius to posit a preconception of non-sensible entities like atoms, given that preconceptions are passively formed by sense-experiences. I provide two alternate ways for understanding vestigia notitiai, either of which allows Lucretius to hold a strictly empiricist account of preconceptions.
I support my interpretation with an account of analogical argument in Epicurus. As with Lucretius, however, there is a tendency to think that analogies are merely illustrative in Epicurus (Long and Sedley 1987: 1:42). I show that this is not the case with a close reading of his arguments for the atomic minimum (ad Hdt. 57-59). Analogy from the perceptible to the non-evident lays the cognitive groundwork to justify Epicurus’ arguments from inconceivability, a regular component of his method, and evidence from Philodemus’ On signs confirms and informs my reconstruction.
Mind and Matter