In the Law of Success by Napoleon Hill, Hill relates back to William James. William James was a Psychologist and Philosopher. He wrote ‘The Principles Of Psychology’. He wrote about habit and instinct. Just before christmas I ordered ‘Psychology’ (an edited version of his greater work) and ‘Talks to Teachers’ ( a book created from a few public lectures on Psychology to the Cambridge teachers). Both books arrived yesterday and I’ve been devouring them over the last 24 hours.

More info on William James - William James at Wikipedia
William James Photos and Bio