Best known for pragmatism, functionalism, and James-Lange Theory of Emotion, William James (1842-1910), was an American philosopher and psychologist famous for his pragmatic philosophy. His thoughts are imparted among the books he wrote: The Principles of Psychology, (1890) The Will to Believe and Other Essays in Popular Philosophy, (1897) The Varieties of Religious Experience, (1902) and Pragmatism (1907).

He played an important role in establishing American experimental psychology, but his strength as a thinker lay in his reflective description of thought, motivation and mental capacity.