in a sense, post modernism is impossible to define as it has no coherence or unity.
the term was first applied to particular approaches the creative arts in the 70s, and as the term suggests, its a radical rejection of modernism.
postmodernism questions the validity of modernist* theories, one the grounds they are simply the product of mistaken beleif in what human reason is and can do. we may think we are objective, rational, able to look at our world and describe what it actually is, analyse it and what makes it tick, and suggest ways of making it tick faster or better. but this is a delusion for two main reasons;
1) what we claim as objective knowledge about society is very often just a way of getting power over other people. we decide was makes 'true' knowledge and then control access to it. this can range from education to women to assuming western democracy is the most civilised
2) we are all prisoners of language. we can know most things only indirectly, and only through words.
* modernism is was movement from roughly 1890-1950. it was the idea that people shared a level of universal experience, regardless of where or when they were living.
examples of modernist beleifs are
its possible to acheive truth as meaning transcends society, eg killing is wrong
in the modernist age it is possible to get a grasp of reality, to understand it
science has proven there is certain truths in the world we live, ie gravity.
the idea society is progressing towards better things, ie technology and science
