“Because of the "all-or-none" character of nervous activity, events and the relations among them can be treated by means of propositional logic. It is found that the behaviour of every net can be described in these terms, with the addition of more complicated logical means for nets containing cycles; and that for any logical expression satisfying certain conditions, one can find in net behaving ever fashion it describes.”
Source: A logical calculus of the ideas immanent in nervous activity (1943), p. 115
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Warren S. McCulloch 6
American neuroscientist 1898–1969Related quotes

Principles of Mathematics (1903), Ch. I: Definition of Pure Mathematics, p. 3
1900s
Anatol Rapoport. "Cycle distributions in random nets." The bulletin of mathematical biophysics 10.3 (1948): 145-157.
1940s

Quote from Van Doesburg's text 'Towards elementary plastic expression', as cited in Material zur elementaren Gestaltung, G-1, July 1923; as quoted in 'Theo van Doesburg', Joost Baljeu, Studio Vista, London 1974, p. 141
1920 – 1926

Notations de Logique Mathématique (1894), p. 173, as quoted in "The Mathematical Philosophy of Giuseppe Peano" by Hubert C. Kennedy, in Philosophy of Science Vol. 30, No. 3 (July 1963)

Attributed in posthumous publications, Einstein and Religion (1999)
Context: I have found no better expression than "religious" for confidence in the rational nature of reality as it is accessible to human reason. Wherever this feeling is absent, science degenerates into uninspired empiricism. … I cannot accept your opinion concerning science and ethics or the determination of aims. What we call science has the sole purpose of determining what is. The determining of what ought to be is unrelated to it and cannot be accomplished methodically. Science can only arrange ethical propositions logically and furnish the means for the realization of ethical aims, but the determination of aims is beyond its scope. At least that is the way I see it.
Letter to his friend Maurice Solovine (1 January 1951) p. 120

1880s, Agnosticism (1889)
Context: Agnosticism is not properly described as a "negative" creed, nor indeed as a creed of any kind, except in so far as it expresses absolute faith in the validity of a principle which is as much ethical as intellectual. This principle may be stated in various ways, but they all amount to this: that it is wrong for a man to say that he is certain of the objective truth of any proposition unless he can produce evidence which logically justifies that certainty. This is what agnosticism asserts; and, in my opinion, it is all that is essential to agnosticism. That which agnostics deny and repudiate as immoral is the contrary doctrine, that there are propositions which men ought to believe, without logically satisfactory evidence; and that reprobation ought to attach to the profession of disbelief in such inadequately supported propositions. The justification of the agnostic principle lies in the success which follows upon its application, whether in the field of natural or in that of civil history; and in the fact that, so far as these topics are concerned, no sane man thinks of denying its validity.