  The first argument begins with the assumption (call it P1) that nothing that is itself by itself is in (or among) humans (Parmenides 133c3–6). This assumption reflects a particular understanding of what Separation requires, a conception that is emphasized in the dialogues of the middle period (see Symposium 211a8–b1 and Timaeus 52a1–3—for discussion, see Rickless (2007, 19–20)). Parmenides then adds, and provides instances of, two further premises, P2 and P3: