industries for their savings, acquire titles to part of the capital in Department I by supplying the difference between investment in Department I and its own saving.[46] For any increase in the stock of capital of both departments taken together, required by technical progress and demand conditions, there is an appropriate amount of saving, and so long as the total accumulation required and total saving fit, there is no breakdown. But here we find the clue to the real contradiction. These quantities might conceivably fit, but there is no guarantee that they will. If the ratio of saving which the capitalists (taken together) choose to make exceeds the rate of accumulation dictated by technical progress, the excess savings can only be 'capitalised' if there is an outlet for investment outside the system. (The opposite case of deficient savings is also possible. Progress would then be slowed down below the technically possible maximum; but this case is not contemplated by our author, and it would be irrelevant to elaborate upon it.) Once more we can substitute for a supposed logical necessity a plausible hypothesis about the nature of the real case, and so rescue the succeeding argument. If in reality the distribution of income between workers and capitalists, and the propensity to save of capitalists, are such as to require a rate of accumulation which exceeds the rate of increase in the stock of capital appropriate to technical conditions, then there is a chronic excess of the potential supply of real capital over the demand for it and the system must fall into chronic depression. (This is the 'stagnation thesis' thrown out by Keynes and elaborated by modern American economists, notably Alvin Hansen). How then is it that capitalist expansion had not yet (in 1912) shown any sign of slackening?