The type of writing determines which happens. In societies whose scripts lead to the development of literate elites it strengthens the hold of traditions. A small group becomes responsible for preserving the past. In these societies, learning to read was mixed with another activity-learning the traditional way of doing things. They were unlikely to reflect upon and so undermine it.
Literacy can, however, undermine the authority of tradition.
While literacy was the preserve of those upholding tradition this reflection would not involve questioning the authority of the text. They could reinterpret tradition themselves. Philosophers in other cultures speculated upon these questions but their ideas upheld tradition. The novelty of Greek philosophers was to free these questions from traditional interpretation, creating their own traditions for questioning and criticising customary attitudes, Those forms of social power that depended upon tradition had to adapt or die out. In many parts of Greece, this questioning produced democratic procedures.