The idea of Masonic brotherhood probably descends from a 16th-century legal definition of a brother as one who has taken an oath of mutual support to another. Accordingly, <answer>Masons swear at each degree to keep the contents of that degree secret</answer>, and to support and protect their brethren unless they have broken the law. In most Lodges the oath or obligation is taken on a Volume of Sacred Law, whichever book of divine revelation is appropriate to the religious beliefs of the individual brother (usually the Bible in the Anglo-American tradition). In Progressive continental Freemasonry, books other than scripture are permissible, a cause of rupture between Grand Lodges.
Are masons allowed to divulge the secrets of each degree?
Masons swear at each degree to keep the contents of that degree secret