"Think For Yourself, Schmuck!", one of the central dogma/catma of Discordianism.
Similar and related phrases in this context are "Question Authority, Think for Yourself", "Black
Sheep are still
Sheep", "The Map is not the Territory", "Don't Eat the Menu!", "Do What Thou Wilt Shalt Be The Whole Of The Law--But Remember Nobody Likes an
Asshole!", "A Conclusion is Simply where you Stopped Thinking" and of course being forbidden to believe anything that is written.