Philosophy itself often appears to us as a consciousness-altering experience, a new version of the perception of our Universe, sometimes so radical that it becomes potentially dangerous. Thus, philosophy can be considered as a psychoactive substance, while the role of psychoactive substances themselves in philosophy is not obvious. In this more or less chronological overview, we will shed light on the history of prominent Western philosophers who took psychedelic drugs and explore how this may have affected their ideas - that is, how hallucinogens influenced philosophy.