Sidebar on Lord Kelvin

Lord Kelvin, a major 19th Century scientist (equivalent to Einstein) who is responsible for the Second Law of Thermodynamics (the one about entropy), had a couple of things to say about measurement and quantification. To begin with, he noted the central axiom of science and scientific method:


The obvious corollary to this is that you can’t know something until you’ve measured it.

Kelvin’s second contribution here is a statement that is cut into the stone, now hidden by ivy, over the main doors of most engineering schools in the world:

“I often say that when you can measure what you are speaking about, and can 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 meager and unsatisfactory kind.”

Now this may sound both hopelessly geeky and hopelessly in conflict with the unmeasurable subjective intuitions that are central to making and enjoying music and art. However, it has been my experience that Kelvin is right on both counts. The thing to keep in mind is that he demands some humility from us: he was aware that we don’t know very much (lots of stuff is really tough and/or impossible to measure) and therefore much of what we think we know is meager and unsatisfactory.

Mathphobes, and I am speaking from personal experience here, are especially good at resisting or denying the clarifying test of mathematical expression, preferring to trust to luck, intelligence and talent as substitutes for knowledge. Well, you can’t be lucky, smart, and talented all the time, and when you run out of these wonderful things, you’re really going to need knowledge, and some of the best knowledge of all is the knowledge acquired through numbers learned from measurements!

Now that I’ve said that, rest assured that I know very well that many incredibly important things defy measurement and quantification. Love would be a good example, and measuring and quantifying love seems like a truly silly and probably counterproductive thing to try to do, especially in a romantic situation and in spite of Elizabeth Barrett Browning’s sonnet that begins, “How do I love thee? Let me count the ways.”

I have found Kelvin’s principles to be true, in art and love as well as in science. I’m a long way from knowing very much about love, and in many respects my poorly quantified sense of music is truly equally meager and unsatisfactory. It just may not be possible for us humans to do any better! See what I mean about humility?