How did Phillip K Dick became a post modernism writer?

Philip K. Dick was a product of his times where many of his generation questioned the cultural mores through the novels written . Many of PKD's novels incorporate themes of skepticism in his books where commonly accepted norms are brought into question . PKD brought to light through his novels the dichotomy of a government or police force that can not be trusted but portrays itself as being beyond reproach such as in "The Penultimate Truth" and "A Scanner Darkly" .