In "The General Theory of Employment, Interest and Money", Chapter 6 The Definition of Income Saving and Investment, John Maynard Keynes says:
Income = value of output = consumption + investment.
Saving = income - consumption.
Therefore saving = investment.
The equivalence between the quantity of saving and the quantity of investment emerges from the bilateral character of the transactions between the producer on the one hand and, on the other hand, the consumer or the purchaser of capital equipment.
And in Chapter 7 The Meaning of Saving and Investment Further Considered says:
In the previous chapter saving and investment have been so defined that they are necessarily equal in amount, being, for the community as a whole, merely different aspects of the same thing
Thus the old-fashioned view that saving always involves investment, though incomplete and misleading, is formally sounder than the new-fangled view that there can be saving without investment or investment without 'genuine' saving.
In fact, all chapter 6 and 7 is about that saving is equals to investment. But later, in other chapters, when Keynes talk about lack of investments or to much liquidity-preference, it sounds like really there are some savings that not involves investment. Morover, in Chapter 23 Notes on Mercantilism, the Usury Laws, Stamped Money and Theories of Under-Consumption says:
It is impossible to study the notions to which the mercantilists were led by their actual experiences, without perceiving that there has been a chronic tendency throughout human history for the propensity to save to be stronger than the inducement to invest. The weakness of the inducement to invest has been at all times the key to the economic problem.
But if saving is equals to investment, then don't matter the supposed difference between propensity to save and inducement to invest.
In general, I find very confusing all passages of this book about investment because some time looks like investment and saving are the same (so there can't be saving without investment and can't be investment without 'genuine' saving) and others times looks like invest and saving are differents (so there can be saving without investment or investment without 'genuine' saving).
Can someone clarify this concepts according Keynes "The General Theory of Employment, Interest and Money"?