For the Frankfurt School of philosophers, struggling in the 1930's and 1940's to find alternatives to Marxism and capitalism, the great problem of society was 'alienation'. Economic rivalries and short-sighted materialism sundered society. Individuals felt dissatisfied and unrooted. Martin Heidegger proposed a strategy for coping: accepting our existence between birth and death as the only immutable thing about us and tackling life as a project of self-realisation, of 'becoming'. Who we are changes as a project unfolds. This 'existentialism' represented the retreat of intellectuals into the security of self-contemplation, in revulsion from an uglified world.