Earlier quoted context omitted.
Keynes's ideas also fail all over the globe. Saving and investing is what grows an economy.
Saving doesn't grow the economy, pretty much by definition as was already pointed out. (Real) investment, in the sense of building up new productive capacity, is an important part of growing the economy. However, investment at least by the private sector cannot thrive in a vacuum. It needs a context of either existing or plausible demand. If the demand is missing, you'd be a fool to spend money on increasing producti…
Saving goes hand in hand with investment since by putting money in the bank it can be borrowed by entrepreneurs and they can hopefully do something productive with it. Merely spending it doesn't have that effect.