Self-directed learning is a core theoretical construct of adult learning. Importantly, self-directed learning represents a fundamental meta-competence for living and working in our increasingly complex and unpredictable world. Nonetheless, the construct of self-directed learning has become obfuscated. In order to redress this concern, this theoretical paper presents a model of "Four Dimensions of Self-Directed Learning." The present paper highlights two original theoretical points (1) that there are four key dimensions of the self-directed learning construct, and (2) responsibility and self-regulation required for self-directed learning is not equivocal to that required for teacher-directed learning. Theoretically, the latter point may, in part, explain why practice of years of teacher-directed learning in formal schooling does not prepare persons for competent self-directed learning in adulthood. So, adult education represents a primary opportunity to foster self-directed learning competence in adult learners, but adult education practitioners must be ready to provide support to facilitate the process.