One of John Maynard Keynes’ more famous quotes is his description of economics as “an apparatus of the mind.”

While the statement is frequently repeated, it is rarely cited.  In my hunt for where the quote came from, I stumbled across a book by Keynes’ father, John Neville Keynes. Published in 1897, the elder Keynes writes:

[E]conomics is of necessity a science of cause and effect. The economist cannot help endeavoring to trace the effects to their causes, and to assign to causes their effects. But the detection of causal connexion needs the assistance of some apparatus of reasoning, inductive or deductive or a combination of these. Mere reflective observation cannot possibly give the requisite insight.

Twenty five years later, John Maynard Keynes, provides his famous description of economics in the first words of an introduction to Hubert Henderson’s Supply and Demand:

The Theory of Economics does not furnish a body of settled conclusions immediately applicable to policy. It is a method rather than a doctrine, an apparatus of the mind, a technique of thinking, which helps its possessor to draw correct conclusions. It is not difficult in the sense in which mathematical and scientific techniques are difficult; but the fact that its modes of expression are much less precise than these, renders decidedly difficult the task of conveying it correctly to the minds of learners.