A group of people called the Kalamas lived in a town called Kesaputta in ancient India. They were fed up with wandering teachers continually coming into their town, and "expounding their own doctrines, and the doctrines of others they despise, revile and pull to pieces."

They asked the Buddha who was also visiting, how they could tell who was telling the truth.

He gave them this advice - which I lay before you today:

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 in anything because it is spoken and rumoured by many.

Do not believe in anything simply because it is found 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 benefit of one and all then accept it and live up to it.

From the Kalama Sutta in the Anguttara Nikaya.