Approximately 2,600 years ago when the Buddha was traveling through the Kosala region of India, he happened upon a group of people known as the Kalamas.  The Kalama Sutra records the following sermon which he spoke to them:

Rely not on the teacher/person, but on the teaching. Rely not on the words of the teaching, but on the spirit of the words. Rely not on theory, but on experience.

Do not believe in anything simply because you have heard it. Do not believe in traditions because they have been handed down for many generations. Do not believe anything because it is spoken and rumoured by many.

Do not believe in anything because it is written in your religious books. Do not believe in anything merely on the authority of your teachers and elders. But after observation and analysis, when you find that anything agrees with reason and is conducive to the good and the benefit of one and all, then accept it and live up to it.