 In that state, dramatically described at 52d4–53c3, the filled space that is the receptacle undergoes constant, erratic motion: it is subject to forces (dunameis, 52e2) that are dissimilar to and out of balance with each other, and thus, as each spastic movement produces its chain of spastic reactions, it is perpetually unstable (52e1–5). These motions may accidentally produce manifestations that to a would-be observer look like fire or any of the so-called four elements, or “kinds” (genê). Timaeus calls these manifestations “traces” (53b2) of the four kinds, and states that even as inarticulate traces, they tended to behave in the ways in which the subsequently articulated kinds would come to behave by necessity: each trace type would gather to its own region, with the heavier to one region and the lighter to another. These migrations are the effect of the ceaseless agitation of the receptacle, which acts like a “winnowing sieve” (52e6), separating the heavy from the light. The result is a pre-cosmic inchoate stratification of these traces, which anticipates the (perpetually incomplete, 58a2–c4) stratification of the finished universe.