“Ifs and buts could erode the soundest of principles.”

Context: There is no reason why an extraphysical general principle is necessarily to be avoided, since such principles could conceivably serve as useful working hypotheses. For the history of scientific research is full of examples in which it was very fruitful indeed to assume that certain objects or elements might be real, long before any procedures were known which would permit them to be observed directly.

The Structure of the Universe: An Introduction to Cosmology (1949)
Context: Another interesting feature of the Einstein universe is that in principle it could be circumnavigated by a ray of light... it is unlikely that the rays would converge with sufficient accuracy. Nevertheless it is interesting to consider the possibility that some of the stars and nebulae which we see may after all be only optical ghosts.<!--p.79

Source: Twelve Years a Slave

The Philosophical Emperor, a Political Experiment, or, The Progress of a False Position: (1841)
Context: His majesty recollected the celebrated quack doctor, who when asked why his patrons were more numerous than those of regular practitioners, replied, that he was patronised by the fools, who are numerous in every community, while regular physicians are patronised by the wise, who are few. His majesty could not see why the principle was not applicable to politics. He resolved to try it. He would so govern as to be patronised by the numerous class, and leave the desires of the few to be regarded by some future emperor, who should choose to make so unpromising an experiment.

Source: The Riverworld series, To Your Scattered Bodies Go (1971), Chapter 23 (p. 172)

Source: The Logic of Scientific Discovery (1934), Ch. 1 "A Survey of Some Fundamental Problems", Section I: The Problem of Induction
Context: A principle of induction would be a statement with the help of which we could put inductive inferences into a logically acceptable form. In the eyes of the upholders of inductive logic, a principle of induction is of supreme importance for scientific method: "… this principle", says Reichenbach, "determines the truth of scientific theories. To eliminate it from science would mean nothing less than to deprive science of the power to decide the truth or falsity of its theories. Without it, clearly, science would no longer have the right to distinguish its theories from the fanciful and arbitrary creations of the poet's mind."
Now this principle of induction cannot be a purely logical truth like a tautology or an analytic statement. Indeed, if there were such a thing as a purely logical principle of induction, there would be no problem of induction; for in this case, all inductive inferences would have to be regarded as purely logical or tautological transformations, just like inferences in inductive logic. Thus the principle of induction must be a synthetic statement; that is, a statement whose negation is not self-contradictory but logically possible. So the question arises why such a principle should be accepted at all, and how we can justify its acceptance on rational grounds.

Source: Kodokan Judo (1882), p. 23
Context: In randori we learn to employ the principle of maximum efficiency even when we could easily overpower an opponent. Indeed, it is much more impressive to beat an opponent with proper technique than with brute force. This lesson is equally applicable in daily life: the student realized persuasion backed up by sound logic is ultimately more effective than coercion.

Address to Civil, Naval, Military and Air Force Officers of Pakistan Government, Karachi (11 October 1947)