When investment collapses the question then becomes: how can that private sector investment be restored? Is there a substitute for it in the meantime to increase employment, income and output?
The answer is yes. And consumption is certainly one factor, but not the only one. In fact, the major Keynesian method to restore the health of economies historically has been stimulus programs that take the form of public infrastructure/public investment.Social Democracy for the 21st Century
The Essence of Keynesianism is Investment