Reason is a faculty which is sufficient for its own purposes. Its operations originate from itself, and proceed directly to the end proposed; whence those actions, which are directed by this faculty of reason, are called right actions, as expressive of that rectitude and simplicity with which they are performed.

Marcus Aurelius, Meditations
https://coldewey.cc/2011/07/reason-is-a-faculty-which-is-sufficient-for-its/ ยป