The Kalama Sutta

Although this discourse is often cited as the Buddha's carte blanche for following one's own sense of right and wrong, it actually says something much more rigorous than that. Traditions are not to be followed simply because they are traditions. Reports (such as historical accounts or news) are not to be followed simply because the source seems reliable. One's own preferences are not to be followed simply because they seem logical or resonate with one's feelings. Instead, any view or belief must be tested by the results it yields when put into practice; and — to guard against the possibility of any bias or limitations in one's understanding of those results — they must further be checked against the experience of people who are wise. The ability to question and test one's beliefs in an appropriate way is called appropriate attention. The ability to recognize and choose wise people as mentors is called having admirable friends.

---Thanissaro Bhikkhu, in the Preface to his translation of The Kalama Sutta---