“Between 1937 and 1941, Dobzhansky went from being able to allow for the possibility of evolutionary mechanisms other than those he favored to a position in which everything that did not fit his definition of evolution was rejected.
In the midst of his outpouring of anger at and dismissal of Goldschmidt, Dobzhansky neglected to consider the fact that while Goldschmidt's systemic mutations may not have been observed, neither had the mechanisms of speculation that he, or anyone else, for that matter, had proposed. …it was and still is the case that, with the exception of Dobzhansky's claim about a new species of fruit fly, the formation of a new species, by any mechanism, has never been observed.”
Jeffrey H. Schwartz, Sudden Origins: Fossils, Genes, and the Emergence of Species (1999)
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Theodosius Dobzhansky 9
geneticist and evolutionary biologist 1900–1975Related quotes

The Evolution of Physics (1938) (co-written with Leopold Infeld) <!-- later published by Simon & Schuster (1967) -->
1930s
Context: Physical concepts are free creations of the human mind, and are not, however it may seem, uniquely determined by the external world. In our endeavor to understand reality we are somewhat like a man trying to understand the mechanism of a closed watch. He sees the face and the moving hands, even hears its ticking, but he has no way of opening the case. If he is ingenious he may form some picture of a mechanism which could be responsible for all the things he observes, but he may never be quite sure his picture is the only one which could explain his observations. He will never be able to compare his picture with the real mechanism and he cannot even imagine the possibility or the meaning of such a comparison. But he certainly believes that, as his knowledge increases, his picture of reality will become simpler and simpler and will explain a wider and wider range of his sensuous impressions. He may also believe in the existence of the ideal limit of knowledge and that it is approached by the human mind. He may call this ideal limit the objective truth.

On Joseph McCarthy (November 30, 1954), in Fulbright of Arkansas: The Public Positions of a Private Thinker (1963)

Third Thesis
Idea for a Universal History from a Cosmopolitan Point of View (1784)

"Price Flexibility and Output Stability: An Old Keynesian View" (1993)

1920s, Viereck interview (1929)
Source: 1980s, Evolutionary Economics, 1981, p. 44