William James was an American philosopher and psychologist who lived in the 1800s and early 1900s. He studied how people think and feel and wrote a lot about it. He coined the term 'stream of consciousness' which means that all of your thoughts, feelings, and experiences are like a river or stream running through your mind. He also wrote about emotions and how they can influence your behavior and choices. His famous book, 'The Principles Of Psychology', was one of the first works to explore these areas in a scientific way. He argued that free will is a part of life and that we can choose to pursue meaningful goals. His work helped to shape the modern field of psychology.