Treaties on Money (Keynes,1930): Keynes stresses the importance of 'animal spirits' in financial markets:

'...the vast majority of those who are concerned with the buying and selling of securities know almost nothing whatsoever about what they are doing. They do not posses even the rudiments of what is required for a valid judgement, and are the prey of hopes and fears easily aroused by transient events and as easily dispelled. This is one of the odd characteristics of the capitalist system under which we live, which , when we are dealing with the real world, is not to be overlooked'