Spontaneous directed motion, a hallmark of cell biology, is unusual in classical statistical physics. Here we study, using both numerical and analytical methods, organized motion in models of the cytoskeleton in which constituents are driven by energy-consuming motors. Although systems driven by small-step motors are described by an effective temperature and are thus quiescent, at higher order in step size, both homogeneous and inhomogeneous, flowing and oscillating behavior emerges. Motors that respond with a negative susceptibility to imposed forces lead to an apparent negativetemperature system in which beautiful structures form resembling the asters seen in cell division.nonequilibrium structures | symmetry breaking | emergent phenomenon | soft condensed matter S pontaneous directed motion driven by active processes is crucial to biology. Such motion is only possible because the cell is a far-from-equilibrium many-body system. The cytoskeleton of eukaryotic cells is built, maintained, and adaptively reorganized through active transport and force generation powered by ATP hydrolysis. Oscillations of the mitotic spindle during cell division (1) and cytoplasmic streaming (2) dramatically illustrate that the cell is not at equilibrium. Driven motions of cells are also important at higher levels of organization in living things ranging from mechanosensation (3) to the developmental processes in which the genetic code unfolds to create a multicellar organism (4). Sustained spontaneous collective motion is quite remarkable in many-body physics. Superfluidity and superconductivity are examples of metastable states of motion made possible by quantum statistics. The biological example provided by the cytoskeleton is seemingly quite different, leading not to infinitely long-lived states but to ones that go away when the cell is depleted of fuel and dies. Nevertheless, like the quantum examples, the motion of the cytoskeleton is an emergent many-body phenomenon reflecting broken symmetries.Here we explore the origin of spontaneous collective motion for systems of many interacting biomacromolecules with motordriven active processes using a systematic perturbative expansion of the many-body master equation treating nonequilibrium motorized processes. We model the motors as generating a time series of isotropic kicks on the constituents of a many-body assembly. Earlier (5) we showed that quite generally the corresponding master equation, when expanded to the lowest order in the kick step size, yields an effective temperature, T eff , which explicitly depends on the total motor activity and on the way in which motors respond to imposed forces. A system described by an effective temperature alone (6-8) cannot undergo spontaneous directed motion unless it is quantum mechanical so that spatial and momentum degrees of freedom are coupled by the uncertainty principle. Pursuing the expansion to higher order, however, reveals the possible emergence of spontaneous directed collective motion quite generally from a quiescent homogene...