Joan Robinson published Introduction to the Theory of Employment in 1937 as a simplified account of the main principles of Keynes' General Theory. Speaking down to her audience, she prefaces the book by writing "I have done my best to resist the temptation to address my colleagues over the heads of the audience for which this book is properly intended."
The part of the book I focus on here is Robinson's description of the relation between savings and investment. It's a topic at the heart of a lot of debates still ongoing in economics. Robinson explains that
"Saving depends upon income, and income depends upon the rate at which investment goods are being produced... Saving is equal to investment, because investment leads to a state of affairs in which people want to save. Investment causes incomes to be whatever is required to induce people to save at a rate equal to the rate of investment. The more willing people are to save, the lower is the level of income corresponding to a given rate of investment, and the smaller the increase in income brought about by a given increase in the rate of investment."
However, many mainstream economists disagree with this view (sometimes without realizing it -- we're implicitly taught a view that doesn't make sense when you think about it):
"Some writers appear to disagree with this view. Savings, they say, are devoted to buying securities, and if saving increases there is an increased demand for securities. New securities are issued in order to finance investment, and therefore an increase in saving leads to an increase in investment. This argument sinks at the first step, for, since an individual, by increasing his own savings, reduces the savings of others, he does not add to the rate of saving of the community, and therefore does not add to the demand for securities. But the initial error leads to a further complication. If saving directly caused investment, it would be very difficult to see how unemployment could possibly occur, and such writers, in order to provide an explanation of unemployment, usually fall back on the notion of "hoarding". If an individual saves, they say, and buys securities with his new wealth, investment automatically increases, but if he puts his new wealth into money, that is, hoards it, there is no corresponding investment. But this is simply an error. The saving of the individual is not a cause of investment in either case, and the distinction does not arise... The individual saver has no direct influence on the rate of investment, whether he buys securities or not."
