Give me a dozen healthy infants, well-formed, and my own specified world to bring them up in and I’ll guarantee to take any one at random and train him to become any type of specialist I might select—doctor, lawyer, artist, merchant-chief and, yes, even beggar-man and thief, regardless of his talents, penchants, tendencies, abilities, vocations, and race of his ancestors. (1930)

If diphtheria is a disease caused by a microorganism, it is essential that three postulates be fulfilled. The fulfilment of these postulates is necessary in order to demonstrate strictly the parasitic nature of a disease:
1) The organism must be shown to be constantly present in characteristic form and arrangement in the diseased tissue.
2) The organism which, from its behaviour appears to be responsible for the disease, must be isolated and grown in pure culture.
3) The pure culture must be shown to induce the disease experimentally.
An early statement of Koch's postulates.

Man's unconscious... contains all the patterns of life and behaviour inherited from his ancestors, so that every human child, prior to consciousness, is possessed of a potential system of adapted psychic functioning.

On consideration, it is not surprising that Darwin's finches should recognize their own kind primarily by beak characters. The beak is the only prominent specific distinction, and it features conspicuously both in attacking behaviour, when the birds face each other and grip beaks, and also in courtship, when food is passed from the beak of the male to the beak of the female. Hence though the beak differences are primarily correlated with differences in food, secondarily they serve as specific recognition marks, and the birds have evolved behaviour patterns to this end.

Plasticity is a double-edged sword; the more flexible an organism is the greater the variety of maladaptive, as well as adaptive, behaviors it can develop; the more teachable it is the more fully it can profit from the experiences of its ancestors and associates and the more it risks being exploited by its ancestors and associates.

Psychologists must cease to be content with the sterile and narrow conception of their science as the science of consciousness, and must boldly assert its claim to be the positive science of mind in all its aspects and modes of functining, or, as I would prefer to say, the positive science of conduct or behavior.

The experience and behaviour that gets labelled schizophrenic is a special strategy that a person invents in order to live in an unlivable situation.

The striving to achieve an end is … the mark of behaviour; and behaviour is the characteristic of living things.

There is nothing distinctively scientific about the hypothetico-deductive process. It is not even distinctively intellectual. It is merely a scientific context for a much more general stratagem that underlies almost all regulative processes or processes of continuous control, namely feedback, the control of performance by the consequences of the act performed. In the hypothetico-deductive scheme the inferences we draw from a hypothesis are, in a sense, its logical output. If they are true, the hypothesis need not be altered, but correction is obligatory if they are false. The continuous feedback from inference to hypothesis is implicit in Whewell's account of scientific method; he would not have dissented from the view that scientific behaviour can be classified as appropriately under cybernetics as under logic.

While our behavior is still significantly controlled by our genetic inheritance, we have, through our brains, a much richer opportunity to blaze new behavioral and cultural pathways on short timescales.

… and the thousands of fishes moved as a huge beast piercing the water. They appear united, inexorably bound by common fate. How comes this unity?