Who was the pragmatic philosopher and author of a major textbook for emerging discipline psychology?

The pragmatic philosopher and author of a major textbook for the emerging discipline of psychology was William James.

Here's why:

* Pragmatism: James was a leading figure in the philosophy of pragmatism, which emphasizes the practical consequences of ideas and theories.

* Textbook: He wrote "Principles of Psychology" (1890), which was a landmark work that helped establish psychology as a distinct academic discipline.

* Influence: "Principles of Psychology" was widely influential, and it's considered one of the most important books ever written in the field.

Let me know if you'd like to know more about William James or his contributions to psychology!