Einstein on intuition in physics

Using as few hypothetical laws as possible, science attempts to explain relations between observable facts, arriving at them in a deductive manner, that is, in a purely logical way. Physics is customarily referred to as an empirical science and it is believed that its fundamental laws are deduced from experiments, so as to indicate how it differs from speculative philosophy. However, in truth the relationship between fundamental laws and facts from experience is not that simple. Indeed, there is no scientific method to deduce inductively these fundamental laws from experimental data. The formulation of a fundamental law is, rather, an act of intuition which can be achieved only by one who watches empirically with the necessary attention and has sufficient empirical understanding of the field in question. The sole criteria for the truth of a fundamental law is only that we can be sure that the relations between observable events can be logically deduced from it. It follows then that a fundamental law can be refuted in a definite manner, but can never be definitely shown to be correct, as one must always bear in mind the possibility of discovering a new phenomenon that contradicts the logical conclusions arising from a fundamental law.

Experience is, therefore, the judge, but not the generator of fundamental laws. The transition from the facts of experience to a fundamental law often requires an act of free creativity from our imagination, as well as an act of creation of concepts and relations; it would not be possible to replace this act with a necessary and conclusive method...

Albert Einstein, Unpublished Opening Lecture for the Course on the Theory of Relativity in Argentina, 1925

(The full lecture is in Science in Context, Vol. 21, issue 3, pp. 451-459 (2008); posted today on the preprint server as arXiv:0903.2401v1 [physics.hist-ph] . © The Hebrew University, Jerusalem.)