What is it about this paragraph that should have shaken up the psychology “establishment’ of the time?

John B, Watson, known as the “father of behaviorism, was one of psychology’s most colorful and controversial figures, never shy about self-promotion. He was a product of the Chicago school of functionalist thinking, taught there by James Angell.

Watson left Chicago for John Hopkins in 1908 and within a year, because of a scandal, headed the psychology program there. While there he delivered a series of eight lectures at Columbia University. The opening lecture, which he gave in 1913, was entitled “Psychology as the Behaviorist Views It.” To later generations of psychologists, reared in a discipline defining itself as the “science of behavior,” this lecture would become known as the “behaviorist manifesto”. This is your reading assignment this week.

The opening paragraph of Watson’s “manifesto’ is one of psychology’s most quoted passages. What is it about this paragraph that should have shaken up the psychology “establishment’ of the time? Within his “manifesto” what arguments, does he make against the two schools of psychology functionalism and structuralism?