“Q, which would include quantity of space or time or force, in fact almost any kind of quantity.”

—  William Stanley Jevons , The Theory of Political Economy

Preface To The Second Edition, p. 6.
The Theory of Political Economy (1871)
Context: A correspondent, Captain Charles Christie R. E., to whom I have shown these sections after they were printed, objects reasonably enough that commodity should not have been represented by M, or Mass, but by some symbol, for instance Q, which would include quantity of space or time or force, in fact almost any kind of quantity.

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William Stanley Jevons 69
English economist and logician 1835–1882

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