This article discusses the teachers' role in self-directed learning (SDL) -- a central concept in adult education. We explore the use of Socratic questioning to develop critical thinking, which is the outcome of SDL in problem-based learning (PBL). In particular, we analyse 11 adult learners' reflective journals in relation to a Socratic seminar. Findings showed that adult learners value the mutual relationship between the learner and the teacher in managing the learning process. In addition, we suggest a teaching approach where Socratic questioning can facilitate students' SDL. We conclude with implications on its use as a means to initiate the learning goals of a PBL tutorial.