Verhältnis von Experiment und Theorie:
"As early as 1898 Poincare had explicitly denied any justification for the idea of absolute simultaneity, and had proposed the operational definition of simultaneity based on light signals. By 1905 he had the full Lorentz transformations for electrodynamics, including the group property, and had corrected Lorentz’s expression for the current density. Moreover, he wrote:
'It appears that the impossibility of detecting the absolute motion of the Earth by experiment may be a general law of nature; we are naturally inclined to admit this law, which we will call the ‘Postulate of Relativity’ and admit without restriction. Whether or not this postulate, which up to now agrees with experiment, may later be corroborated or disproved by experiments of greater precision, it is interesting in any case to ascertain its consequences.'"
Grand Unified Theory:
"We cannot be content with a simple juxtaposition of formulas that agree with each other by good fortune alone; these formulas must, in a manner of speaking, interpenetrate. The mind will be satisfied only when it believes it has perceived the reason for this agreement, and the belief is strong enough to entertain the illusion that it could have been predicted."
From here: http://www.mathpages.com/home/kmath305/kmath305.htm