Unsuitable as material for the differential calculus

TorgoX on 2004-12-09T23:05:12

Dear Log,

«To say that net output to-day is greater, but the price-level lower, than ten years ago or one year ago, is a proposition of a similar character to the statement that Queen Victoria was a better queen but not a happier woman than Queen Elizabeth — a proposition not without meaning and not without interest, but unsuitable as material for the differential calculus. Our precision will be a mock precision if we try to use such partly vague and non-quantitative concepts as the basis of a quantitative analysis.»

-- from Chapter 4 of John Maynard Keynes's The General Theory of Employment, Interest and Money