John Nash was an economist and mathematician whose influential 27-page doctoral thesis, completed at Princeton University at age 21, fundamentally advanced game theory. He introduced the concept of the Nash equilibrium to predict outcomes from strategic interactions and proved that such an equilibrium must exist in a broad class of games, a breakthrough that had eluded earlier mathematicians. This proof holds true even when players have diverse motivations, such as selfishness, altruism, or spite. In addition to this foundational work, Nash contributed significantly to bargaining theory and made other pioneering advancements in mathematics, earning him the prestigious Abel Prize. He was a co-recipient of the 1994 Nobel Prize for his work on game theory. His life, which included a long and challenging struggle with schizophrenia, was famously documented in the book and subsequent film 'A Beautiful Mind'.