Human Behaviour is Gouerned by Assumptions and Beliefs (What Argyris Calls ‘Theoryin-Use’), Yet Individuals Commonly Explain Their Behauiour in Terms of a (Different) ‘Espoused’ Theory. It is Suggested here that Reflective Practice in Counselling Can Only be Achieued by Counsellors Identifying Their Own Theories-in-Use Through a Process of Critical Thinking. The Task of Counselling in this Process is for the Counsellor to both Become a Critical Thinker and Enable His/her Client to Become One.