• "My original decision to devote myself to science was a direct result of the discovery which has never ceased to fill me with enthusiasm since my early youth - the comprehension of the far from obvious fact that the laws of human reasoning coincide with the laws governing the sequences of the impressions we receive from the world about us; that, therefore, pure reasoning can enable man to gain an insight into the mechanism of the later. In this connection, it is of paramount importance that the outside world is something independent from man, something absolute, and the quest for the laws which apply to this absolute appeared to me as the most sublime scientific pursuit in life". Max Planck in Scientific Autobiography.

• "The most striking - and a unique - feature of the mind is the acceptance and use of things as symbols standing for other things. Symbols may stand for, refer to, or mean other things which may or may not lie within the world of physics.....In this sense we find the mind in computing machines". Richard L. Gregory in Mind of Science

• "Although geometrical representations of propositions in the thermodynamics of fluids are in general use and have done good service in disseminating clear notions in this science, yet they have by no means received the extension in respect to variety and generality of which they are capable." J. Willard Gibbs from his first of three historic publications, "Grahical Methods in the Thermodynamics of Fluids," 1873.

• "The words or the language, as they are written or spoken, do not seem to play any role in my mechanism of thought. The psychical entities which seem to serve as elements in thought are certain signs and more or less clear images which can be 'voluntarily' reproduced and combined .... this combinatory play seems to be the essential feature in productive thought before there is any connection with logical construction in words or other kinds of signs which can be communicated to others". Albert Einstein in a letter to Jacques Hadamard.

In an interview given by James Gleick from "The Life and Science of Richard Feynman", Vintage Books, New York, 1992, pgs 241-225.

• "Visualization - you keep repeating that", he (Feynman) said to another historian, Silvan S. Schweber, who was trying to interview him

  Feynman: "What I am really try to do is bring birth to clarity, which is really a half-assedly thought-out-pictorial semi-vision thing. I would see the jiggle-jiggle-jiggle or the wiggle of the path. Even now when I talk about the influence functional, I see the coupling and I take this turn - like as if there was a big bag of stuff - and try to collect it in away and to push it.It's all visual. It's hard to explain."

  Schweber: "In some ways you see the answer - ?"

  Feynman: "The character of the answer, absolutely. An inspired method of picturing, I guess. Ordinarily I try to get the pictures clearer, but in the end the mathematics can take over and be more efficient in communicating the idea of the picture."

  "In certain particular problems that I have done it was necessary to continue the development of the picture as the method before the mathematics could be really done."