This is lifted from the novel "Alamut" that the game writers used for inspiration. The novel is about a fictionalized version of the Ismaili, a Muslim group that were referred to as assassins by crusaders because they supposedly used a lot of hash (corruption on "Hashashin"). We don't know much about these original assassin's beliefs, because they operated out of a fortress that had its library burned once conquered and so we only know about them through their enemies. The assassins in the book were intended to be an allegorical portrayal of fascists with a very cynical, power hungry leader (this maxim is his own personal philosophy) brainwashing young men to have overwhelming obedience and carry out any violence the leader asked.

That's a very radical anti-liberal maxim to be in a game if you think about it. Civility in shambles.

Was it just me or as the series went on it was hard to see whatever world the Assassins hoped to build? Maybe it was intentional or just the libs being unable to picture a better society, but either way by the time I stopped following the series their politics was basically "We are against the templars".

"Our Creed does not command us to be free; it commands us to be wise."

“Everything is permitted” comes from The Brothers Karamazov I believe and is Dostoevsky basically arguing that if you don’t believe in god, you have no morals and are no better than a mass-murderer. (I don’t like Dostoevsky.)

If you generalize it a tiny bit, you get "Nothing is absolute; everything is possible". And that's basically the foundation of a constructivist philosophy.