The widely publicized quotation attributed to Albert Einstein is a simpler variant
of the following:
“It can scarcely be denied that the supreme goal of all theory is to make the irreducible
basic elements as simple and as few as possible without having to surrender the adequate
representation of a single datum of experience.”
"On the Method of Theoretical Physics" The Herbert Spencer Lecture, delivered at
Oxford (10 June 1933); also published in Philosophy of Science, Vol. 1, No. 2 (April
1934), pp. 163-169.