William James

William James was an American philosopher-psychologist whose 1890 Principles of Psychology remains widely quoted.

Why?

He framed mental processes by their function, not their parts, and gave psychology its enduring “stream of consciousness” metaphor.

• Main figure behind Functionalism: ask what a mental process is for, not what it’s made of
• Treated introspection as serious data without pretending it was clean
• Literary counterpart to Wundt’s lab-bench empiricism