Jencel’s principle of triviality:

Any self-consistent body of knowledge can be reduced to a number of clear elementary postulates and everything else would follow from them. So, any body of knowledge for which it is not immediately clear what these postulates are, is not self-consistent.

Also, the number of those postulates is usually small.

Simply put: if you cannot explain the system using very elementary language and constructs, then there is probably inconsistency in it somewhere.

Example: most religious doctrines, astrology, cryptocurrenciesetc.