An empirical study was conducted measuring the degree to which Greek university students’ understanding of core philosophical concepts (that is, ‘argument’, ‘knowledge’ and ‘ethics’) has been shaped by the material taught in the classroom. The extent of this transition from pre-instructional conceptions to textbook formulations has been investigated through the use of a new questionnaire. Findings indicate that generally, students retain their pre-theoretical understanding of these terms. Within this framework, some formal definitions are closer to common sense (e.g. ‘ethics’) and some others aren’t (e.g. ‘knowledge’). Furthermore, the role of intuitions in this process is been evaluated, leading to the ascertainment that previous philosophical encounters seem to play a crucial role in determining actual understanding.