This interview with an anonymous psychiatrist presents and illustrates the concept of “epistemological trauma,” an event felt as shattering a person's faith in the functioning of his or her own mind. Such shattering results in a sense that one no longer knows anything, that what was believed to be true and real is illusory and unreliable, and that one's very sanity cannot be trusted. Two clinical cases are extensively described, one involving a woman who discovered her marriage of two decades had been based on lies, and the other concerning a man who experienced the sudden loss of his mother when he was a boy. It is argued that all trauma is epistemological trauma.