Lord Kelvin alledgedly said:

“… when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meager and unsatifactory kind; it may be the beginning of knowlege, but you have scarcely thoughts advanced to the stage of science.”

(Dunham & Kruesi, 1983 in Humphrey, 1988, IEEE software)