"Descartes' Error" refers to the idea that emotions play a crucial role in rational decision-making, challenging the traditional view that reason and emotion are separate. This concept is named after the philosopher René Descartes, who famously stated, "I think, therefore I am," suggesting a clear divide between thought and feeling. The term was popularized by neuroscientist Antonio Damasio in his book "Descartes' Error: Emotion, Reason, and the Human Brain." Damasio's research demonstrated that individuals with damage to emotional processing areas in the brain struggle to make effective decisions, highlighting the interconnectedness of emotion and rationality in human behavior.