WE DON'T KNOW WHAT'S GOING ON AND THAT'S EXACTLY WHAT'S HAPPENING. In the face of a critical society that is growing in complexity, in the face of global crises that torture humanity, we cannot think and live in complexity and expect the unexpected. This essay is a plea for an epistemology of complexity. A plea for a global awareness of the dominance of the unexpected in the contemporary world. There is nothing simple, said Gaston Bachelard, there is only the simplified. The epistemology of complexity is thus a challenge for knowledge, a challenge for science and a challenge for all humanity; complexity links us to the world, it is an awakening thought.