The term 'PROVEN POSTULATE' can be broken down into two parts: 'PROVEN' and 'POSTULATE'. The word 'PROVEN' means to have been tested and verified, while the word 'POSTULATE' is a statement that is assumed to be true without proof. The crossword solution for this term is LAW, which stands for a system of rules and regulations that govern a society. LAW is an important part of any society, as it helps to ensure that people are treated fairly and that justice is served.