"Keynes says the crisis comes about through a lack of ‘effective demand’, namely an unaccountable fall in investment and consumption and this causes profits and wages to fall.  Marx says: let’s start with profits.  If profits fall, then capitalists would stop investing, lay off workers and wages would drop and consumption would fall.  Then there would be a lack of effective demand, as Keynesians like to put it, but this would not be due to a drop in ‘animal spirits’, or ‘confidence’ (we often hear that phrase from economists: ‘a lack of confidence’), or even due to ‘too high’ interest rates, but because profits are down.  The problem lies in the nature of capitalist production, not in the finance sector."