"The fundamental qualitative difference between the superconducting and normal ground state wave function is produced when the large degeneracy of the single particle electron levels in the normal state is removed. If we visualize the Hamiltonian matrix which results from an attractive two-body interaction in the basis of normal metal configurations, we find in this enormous matrix, sub-matrices in which all single-particle states except for one pair of electrons remain unchanged. These two electrons can scatter via the electron-electron interaction to all states of the same total momentum. We may envisage the pair wending its way over all states unoccupied by other electrons."

“Relativity, from one viewpoint the beginning of twentieth-century physics, is from another the capstone of classical physics, the final and most elegant variation of the world view initiated by Galileo and Newton. In a sense, after Einstein, classical physics, just as after Mozart classical music, could go no further.”

“How do we get emotions and feelings out of neurons which, presumably, don't have emotions and feelings?”

“The long and imposing list of physicists who had tried or were trying their hand at superconductivity should have given me pause. Even Einstein, in 1922 — before the quantum theory of metals was in place — had attempted to construct a theory of superconductivity. Fortunately, I was unaware of these many unsuccessful attempts. So when John invited me to join him , I decided to take the plunge.”

“Consider a pair of electrons which interact above a quiescent Fermi sphere with an interaction of the kind that might be expected due to the phonon and the screened Coulomb fields. If there is a net attraction between the electrons, it turns out that they can form a bound state, though their total energy is larger than zero. The properties of a noninteracting system of such bound pairs are very suggestive of those which could produce a superconducting state.”