“It is an acknowledged truth in philosophy that a just theory will always be confirmed by experiment.”

Source: Dictionary of Burning Words of Brilliant Writers (1895), P. 163.

Notice sur les Titres et Travaux scientifiques de Pierre Duhem rédigée par lui-même lors de sa candidature à l'Académie des sciences (mai 1913), The Aim and Structure of Physical Theory (1906)

Source: Existence & the Existent

pg 151.
Against Method (1975)

New Pathways in Science: Messenger Lectures 1934 (1947), p. 211.

Source: Autosuggestion : My method (2014), Chapter II. The role of imagination : About the "Dominance of the imagination over the will".

Conjectures and Refutations: The Growth of Scientific Knowledge (1963)
Context: I may illustrate this by two very different examples of human behaviour: that of a man who pushes a child into the water with the intention of drowning it; and that of a man who sacrifices his life in an attempt to save the child. Each of these two cases can be explained with equal ease in Freudian and in Adlerian terms. According to Freud the first man suffered from repression (say, of some component of his Oedipus complex), while the second man had achieved sublimation. According to Adler the first man suffered from feelings of inferiority (producing perhaps the need to prove to himself that he dared to commit some crime), and so did the second man (whose need was to prove to himself that he dared to rescue the child). I could not think of any human behaviour which could not be interpreted in terms of either theory. It was precisely this fact — that they always fitted, that they were always confirmed — which in the eyes of their admirers constituted the strongest argument in favour of these theories. It began to dawn on me that this apparent strength was in fact their weakness.

E. Payne, trans. (1974) Vol. 1, p. 143
Parerga and Paralipomena (1851), On Philosophy in the Universities

Source: The Life of Reason: The Phases of Human Progress (1905-1906), Vol. III, Reason in Religion, Ch. I