Why Intentions Fail to Become Action: A Threshold Account of Action Initiation

People often intend to act, recognize why the action matters, and still do not begin. This article argues that such failures reveal an under-specified transition in psychological theories of behavior: the moment at which intended action becomes capable of onset. Existing theories explain central parts of the action sequence, including intention formation, implementation planning, self-regulation, effort allocation, and habit. Yet behavioral onset is often treated as a downstream consequence of these processes rather than as a transition with its own enabling conditions. This article develops a threshold account of action initiation. On this account, intention can orient the person toward action, but onset occurs only when effective activation exceeds a resistance- and state-sensitive boundary. Initiation, therefore, depends not only on wanting or planning an action but also on readiness, execution compatibility, attentional stabilization, initiation resistance, structured instability, and prior trajectory. Integrating evidence from intention-behavior research, implementation intentions, procrastination, educational delay, health behavior, digital engagement, and within-person variability, the article distinguishes intention from action possibility and onset from persistence. The account generates falsifiable predictions concerning conditional intention effects, nonlinear onset, resistance manipulation, execution compatibility, path dependence, and structured variability. Its contribution is to specify when valued and intended actions become capable of beginning.