Depending on the religion, faith is belief in a god or gods or in the doctrines or teachings of the religion. Informal usage of faith can be quite broad, including trust or belief without proof, and "faith" is often used as a substitute for "hope", "trust" or "belief". Some critics of faith have argued that faith is opposed to reason. In contrast, some advocates of faith argue that the proper domain of faith concerns questions which cannot be settled by evidence. This is exemplified by attitudes about the future, which (by definition) has not yet occurred.