There is one major difference between a philosopher and a prophet.
Most philosophers are rational beings who base their philosophy of life on reason.
In contrast the prophets may or may not be rational or reasonable, however, invariably prophets and spiritual leaders are creatures of extreme. Generally philosophers base their philosophy of life on ethical values. Consequently they preach the path of reasonableness, balance, and moderation. Through their rational thinking, they prefer to eliminate extremes at either end of any spectrum, and consider the correct method, approach, or path to be somewhere in the middle of that spectrum. While this approach is very pragmatic, particularly with regards to social behavior and communal living, it has nothing to do with spirituality.