Our intuition tells us that we, our conscious selves, cause our own voluntary acts. Yet scientists have long questioned this; Thomas Huxley, for example, in 1874 compared mental events to a steam whistle that contributes nothing to the work of a locomotive. New experimental evidence (most notable, work by Benjamin Libet and Daniel Wegner) has brought the causal status of human behavior back to the forefront of intellectual discussion. This multidisciplinary collection advances the debate, approaching the question from a variety of perspectives.