“Since UFO stands for "unidentified flying object", the word ufology means approximately "knowledge about unknown flying objects", and is therefore a "science" whose content is void by definition. Similar considerations hold for parapsychology.”

Source: Eclipse of Reason (1947), p. 12.

Source: The Nature of Geography (1939), p. 139

Civil-suit deposition against the Herring-Curtiss Company (1909), reported in The Dayton News (31 May 1912) http://home.dayton.lib.oh.us/archives/wbcollection/wbscrapbooks1/WBScrapbooks10079.html
Context: My brother and I became seriously interested in the problem of human flight in 1899... We knew that men had by common consent adopted human flight as the standard of impossibility. When a man said, “It can’t be done; a man might as well try to fly,” he was understood as expressing the final limit of impossibility. Our own growing belief that man might nevertheless learn to fly was based on the idea that while thousands of the most dissimilar body structures, such as insects, fish, reptiles, birds and mammals, were flying every day at pleasure, it was reasonable to suppose that man might also fly... We accordingly decided to write to the Smithsonian Institution and inquire for the best books relating to the subject.... Contrary to our previous impression, we found that men of the very highest standing in the profession of science and invention had attempted to solve the problem... But one by one, they had been compelled to confess themselves beaten, and had discontinued their efforts. In studying their failures we found many points of interest to us.
At that time there was no flying art in the proper sense of the word, but only a flying problem. Thousands of men had thought about flying machines and a few had even built machines which they called flying machines, but these were guilty of almost everything except flying. Thousands of pages had been written on the so-called science of flying, but for the most part the ideas set forth, like the designs for machines, were mere speculations and probably ninety per cent was false. Consequently those who tried to study the science of aerodynamics knew not what to believe and what not to believe. Things which seemed reasonable were often found to be untrue, and things which seemed unreasonable were sometimes true. Under this condition of affairs students were accustomed to pay little attention to things that they had not personally tested.

Part II. Ch. 2 : Mathematical Definitions and Education, p. 131
Science and Method (1908)
Context: Every definition implies an axiom, since it asserts the existence of the object defined. The definition then will not be justified, from the purely logical point of view, until we have proved that it involves no contradiction either in its terms or with the truths previously admitted.

Quaestiones subtilissimae de metaphysicam Aristotelis, as translated in: William A. Frank, Allan Bernard Wolter (1995) Duns Scotus, metaphysician. p. 20-21

Anish kapoor in conversation with Heidi Reitmaier in July 2007 in "Anish Kapoor" by Royal Academy Organization.

"The Daring Young Man on the Flying Trapeze"
The Daring Young Man on the Flying Trapeze (1934)
Context: Through the air on the flying trapeze, his mind hummed. Amusing it was, astoundingly funny. A trapeze to God, or to nothing, a flying trapeze to some sort of eternity; he prayed objectively for strength to make the flight with grace.

Max Weber, The Nature of Social Action, 1922