Available energy is the main object at stake in the struggle for existence and the evolution of the world.
Quoted in D'A W Thompson On Growth and Form (Cambridge 1917)
The most ordinary things are to philosophy a source of insoluble puzzles. With infinite ingenuity it constructs a concept of space or time and then finds it absolutely impossible that there be objects in this space or that processes occur during this time... the source of this kind of logic lies in excessive confidence in the so-called laws of thought.
Quoted in B McGuinness, Ludwig Boltzmann, Theoretical Physics and Philosophical Problems, (Dordrecht, 1974) 64.
To go straight to the deepest depth, I went for Hegel; what unclear thoughtless flow of words I was to find there! My unlucky star led me from Hegel to Schopenhauer ... Even in Kant there were many things that I could grasp so little that given his general acuity of mind I almost suspected that he was pulling the reader's leg or was even an imposter.
Quoted in D Flamm. Stud. Hist. Phil. Sci. 14 (1983) 257.
A mathematician will recognise Cauchy, Gauss, Jacobi or Helmholtz after reading a few pages, just as musicians recognise, from the first few bars, Mozart, Beethoven or Schubert.
Quoted in A Koestler, The Act of Creation
Who ... is not familiar with Maxwell's memoirs on his dynamical theory of gases? ... from one side enter the equations of state; from the other side, the equations of motion in a central field. Ever higher soars the chaos of formulae. Suddenly we hear, as from kettle drums, the four beats 'put n = 5.' The evil spirit v vanishes; and ... that which had seemed insuperable has been overcome as if by a stroke of magic ... One result after another follows in quick succession till at last ... we arrive at the conditions for thermal equilibrium together with expressions for the transport coefficients.
In Michael Dudley Sturge, Statistical and Thermal Physics (2003)