The General Theory of Employment, Interest and Money
Total spending, not thrift, sets the level of jobs — and the state can lift it.
In the depths of the Great Depression, Keynes asked a heretical question: what if mass unemployment isn't a temporary glitch the market will fix on its own — but a trap an economy can fall into and stay in?
The big idea
Classical economics said gluts and unemployment cure themselves: prices and wages fall until everyone willing to work finds a job. Keynes said this can fail. What a society produces — and how many people it employs — depends on how much everyone, all together, is willing to spend. He called that total spending “effective demand.” If demand is too low, factories sit idle and workers stay jobless, and nothing automatically puts it right.
Worse, spending feeds on itself. The dollar you spend becomes someone's income; they spend part of it, which becomes someone else's income, and on it goes — so one dollar of new spending lifts total income by several dollars. That is the “multiplier.” The catch runs in reverse too: when everyone cuts back at once, the multiplier works backward and the slump deepens. Keynes's conclusion was radical for its time — in a deep slump, the government should spend to fill the gap that private spending has left.
How it came about
Keynes was the most famous economist of his age — a Cambridge don, a Bloomsbury aesthete, a speculator, and the man who had warned in 1919 that the punishing reparations of the Versailles Treaty would wreck Europe. As the Depression ground on through the 1930s, with a quarter of workers idle and orthodox economics still prescribing patience and balanced budgets, he set out to overturn the theory itself.
Published in 1936 and aimed squarely at fellow economists, The General Theory is famously hard going; Keynes himself called reading it “a long struggle of escape” from old habits of thought. It split the profession — and within a decade remade it, a turn so complete that it is simply called the Keynesian Revolution.
Why it mattered
The book gave governments both a reason and a toolkit to fight depressions and recessions instead of waiting them out — and it changed how we even see an economy. GDP and the national accounts were built to track Keynes's aggregates. For three decades after the war his ideas were the mainstream; they were attacked in the 1970s and revived, forcefully, in the crises of 2008 and 2020. Almost every stimulus package, and every argument over deficits, is in part an argument about Keynes.
A way to picture it
Imagine a town where everyone, suddenly anxious, decides to spend less and save more. The shopkeeper sells less, so she earns less, so she too spends less — and the barber she has stopped visiting can no longer afford the baker, who lets his assistant go… Each person's thrift is perfectly sensible, yet together they talk the whole town into a slump. That is the paradox Keynes saw: what is prudent for one household can be ruinous when everyone does it at once — and the cure is for someone, often the government, to start spending again.
Where it sits
Keynes stands between Adam Smith and the modern discipline. Where Smith (also in this Library) showed how self-interested individuals are coordinated by an invisible hand, Keynes exposed a case where that coordination fails at the level of the whole economy — where each part, acting sensibly, produces a bad outcome together. After him the field split into the microeconomics that refines Smith's world and the macroeconomics he founded. The arguments he started — markets versus management, austerity versus stimulus — are still the spine of economic politics.
Preface — a struggle of escape
The composition of this book has been for the author a long struggle of escape, and so must the reading of it be for most readers if the author's assault upon them is to be successful,—a struggle of escape from habitual modes of thought and expression.
The principle of effective demand (Ch. 3)
The value of D at the point of the aggregate demand function, where it is intersected by the aggregate supply function, will be called the effective demand.
The marginal propensity to consume and the multiplier (Ch. 10)
… so that we can write ΔYw = k.ΔIw, where 1 − 1/k is equal to the marginal propensity to consume. Let us call k the investment multiplier.
It tells us that, when there is an increment of aggregate investment, income will increase by an amount which is k times the increment of investment.
Long-term expectation: animal spirits (Ch. 12)
Even apart from the instability due to speculation, there is the instability due to the characteristic of human nature that a large proportion of our positive activities depend on spontaneous optimism rather than on a mathematical expectation, whether moral or hedonistic or economic.
Most, probably, of our decisions to do something positive, the full consequences of which will be drawn out over many days to come, can only be taken as a result of animal spirits—of a spontaneous urge to action rather than inaction, and not as the outcome of a weighted average of quantitative benefits multiplied by quantitative probabilities.
Concluding notes — the power of ideas (Ch. 24)
The ideas of economists and political philosophers, both when they are right and when they are wrong, are more powerful than is commonly understood. Indeed the world is ruled by little else.
Practical men, who believe themselves to be quite exempt from any intellectual influences, are usually the slaves of some defunct economist. Madmen in authority, who hear voices in the air, are distilling their frenzy from some academic scribbler of a few years back.