Life is short. This indisputable fact of existence has driven human ingenuity since antiquity, whether through efforts to lengthen our lives with medicine or shorten the amount of time we spend on work using technology. Alongside this struggle to manage the pressure of life's ultimate deadline, human perception of the passage and effects of time has also changed. This book examines a range of material—from Hippocrates to Run Lola Run—to put forth a new conception of time and its limits that, unlike older models, is firmly grounded in human experience. The author's analysis of the roots of the word time connects it to the temples of the skull, demonstrating that humans first experienced time in the beating of their pulses. Tracing this corporeal perception of time across literary, religious, and philosophical works, the author concludes that time functions as a kind of sixth sense—the crucial sense that enables the other five. The book is a meditation on life's inexorable brevity.