This dissertation explores the phenomenology and folk theory of willpower, critically assesses existing scientific theories of willpower that seek to explain the phenomenology and folk theory, and proposes a new scientifically useful theory of willpower. Earlier theories reliant upon such mechanisms or techniques as control of attention, rulemaking and private side bets are shown to be inadequate to explain crucial features of certain behavioral performance deemed to be the exhibition of willpower. This dissertation sets out to a new theory capable of explaining these key features of willpower in terms of a new model of private side bets involving the staking of status ascriptions of strength of will upon the success of the relevant behavioral performances.