لا يتحقق إثبات القانون حين تتشكّل الفكرة الأولى عنه، ولا حين تُدرَك دلالته، بل حين تؤكّده نتائج التجربة.

“The establishment of a law, moreover, does not take place when the first thought of it takes form, or even when its significance is recognised, but only when it has been confirmed by the results of the experiment.”Dmitri Mendeleev