How and why do academics, like Heidegger, experience the temptation of “radicality” by pledging allegiance to totalitarian or extreme political systems? This is what we explore here, mainly through the case of Heidegger, but also through those who were involved in Stalinism before moving away from it. Several elements allow us to explain these investments: the feeling of going in the direction of history, the need for hope, a taste for violence, the desire to see one’s ideas implemented, the concern for oneself, and the prevalence in theoretical thought of a concern for the collective over the subject. Looking back on these radical experiences is an opportunity to take a step aside and distance oneself from them, which forces one to think differently about political engagement.