“Of the contributions made during the essayist period three call for notice: Weismann deserves mention for his useful work in asking for the proof that "acquired characters" or, to speak more precisely, parental experience can really be transmitted to the offspring. The ocurrence of progressive adaptation by transmission of effects of use had seemed so natural to Darwin and his contemporaries that no proof of the physiological reality of the henomenon was thought necessary. Weismann's challenge revealed the utter inadequacy of the evidence on which the beliefs were based. They are doubtless isolated observations which may be interpreted as favouring the belief in these transmissions, but such meagre indications as exist are by general consent admitted to be too slight to be of much assistance in the attempt to understand how the more complex adaptive mechanisms arose.”

Source: Mendel's Principles of Heredity (1913), Chapter XV, p. 289.

Section 3 : Work Democracy versus Politics. The Natural Social Forces for the Mastery of the Emotional Plague;
Variant translation: The fact that political ideologies are tangible, active realities does not prove their necessity. The bubonic plague was an extremely potent social reality. But nobody would have argued that, because it existed, it was necessary and nothing should be done about it.
The Mass Psychology of Fascism (1933), Ch. 10 : Work Democracy

Source: Mendel's Principles of Heredity (1913), Chapter XV, p. 289.

Interview with KHAS-TV, Hastings, Nebraska, February 19, 2009. As transcribed verbatim...jt from MSNBC: Keith Olberman's "Countdown" February 20,09.
2009

"Passages from the life of a philosopher", The Belief In The Creator From His Works, p. 402
Passages from the Life of a Philosopher (1864)
Context: In the works of the Creator ever open to our examination, we possess a firm basis on which to raise the superstructure of an enlightened creed. The more man inquires into the laws which regulate the material universe, the more he is convinced that all its varied forms arise from the action of a few simple principles. These principles themselves converge, with accelerating force, towards some still more comprehensive law to which all matter seems to be submitted. Simple as that law may possibly be, it must be remembered that it is only one amongst an infinite number of simple laws: that each of these laws has consequences at least as extensive as the existing one, and therefore that the Creator who selected the present law must have foreseen the consequences of all other laws. The works of the Creator, ever present to our senses, give a living and perpetual testimony of his power and goodness far surpassing any evidence transmitted through human testimony. The testimony of man becomes fainter at every stage of transmission, whilst each new inquiry into the works of the Almighty gives to us more exalted views of his wisdom, his goodness, and his power.

As quoted in "Shockley's Race View called 'Senile, Fascist'" in St. Petersburg Times (8 September 1971) http://news.google.com/newspapers?nid=888&dat=19710908&id=sewNAAAAIBAJ&sjid=vnUDAAAAIBAJ&pg=4930,1230689

Physics and Philosophy (1958)
Context: I remember discussions with Bohr which went through many hours till very late at night and ended almost in despair; and when at the end of the discussion I went alone for a walk in the neighbouring park I repeated to myself again and again the question: Can nature possibly be so absurd as it seemed to us in these atomic experiments?

The Art of Persuasion
Context: This art, which I call the art of persuading, and which, properly speaking, is simply the process of perfect methodical proofs, consists of three essential parts: of defining the terms of which we should avail ourselves by clear definitions, of proposing principles of evident axioms to prove the thing in question; and of always mentally substituting in the demonstrations the definition in the place of the thing defined.