William James (1842 - 1910), most famous for his work - a book named Principles of Psychology, was born in New York in 1842.
His family lived in several countries affording James a multicultural education, including schools in the U.S., England, France, Switzerland, and Germany. He became fluent in five languages by the time he received a medical degree from Harvard University in 1869 and at age 30 he accepted the teaching position at Harvard that launched his outstanding career in psychology.
In 1875 James established at Harvard one of the first psychology demonstration teaching laboratories in the world. His interests were varied, he wrote about habit, consciousness, personality, emotion, and religion. James continued to write, lecture, and travel until his death in 1910 at his country home in New Hampshire.
The publication of his first work, The Principles of Psychology, secured his place in the history books. He initiated the move of psychology away from Philosophy and toward a discipline of science. The application of scientific methods to the study of human psychology is perhaps his greatest donation to the field.
James also wrote Varieties of Religious Experience (1902) that referred to spirituality, health, and psychology. Moreover, William James was instrumental in the founding of Functionalistic psychology.
James emphasized the function of both consciousness and behavior. For him the only valid criterion for evaluating a theory, thought, or act is whether it works. In keeping with his pragmatism, he claimed that psychology needs to employ both scientific and non-scientific procedures. Similarly, on the individual level, sometimes one must believe in free will and at other times in determinism.