The neuroscience of the last 30 years has discovered that our voluntary actions are initiated by certain happenings in our brains well prior to our consciously willing such actions to occur. That finding seems to threaten the common sense view of persons as agents who both cause such actions and are morally responsible for them. This finding also seems to threaten persons deserving retributive punishment for such actions by the criminal law. Three different interpretations of this finding ground three distinct bases for these threats to our conception of ourselves as responsible agents. First, the finding is taken to show that our choices are not free but are determined by certain brain events over which we have no control. Second, the finding seems to show that our choices do not cause the actions they seem to cause; rather, such choices seem to be merely "epiphenomenal" with voluntary actions, that is, co-effects of some common cause in the brain but themselves lacking any causal power over human actions. Third, the finding is taken to show that consciousness does not guide the actions it seems to guide but is merely an accompanying side effect of certain brain events that are the real causes of human actions. Contemporary neuroscience has thus made concrete and scientifically respectable a series of related challenges to our being responsible agents, challenges that have existed speculatively and in the abstract since the rise of Hobbesian materialism. The lecture assesses whether these challenges are more successful in the hands of contemporary neuroscience than they were in the hands of earlier psychologies, be they those of a Hobbes, a Freud, or a Skinner.