Man is said to be a rational being for the reason that he can employ reason in all matters connected with his existence. This process of reasoning is called rationalism which is originally understood in a limited sense as the practice of explaining the supernatural in religion in a way consonant with reason or of treating reason as the ultimate authority in religion. Rationalism has a wider approach. Lord Buddha employed reason in propounding his law. He says in the Kalama Sutta "Do not believe in what you have heard; do not believe in traditions because they have been handed down for many generations; do not believe in anything because it is rumoured and spoken by many; do not believe merely because the written statement of some old sage is produced; do not believe in conjectures; do not believe in that as truth to which you have become attached by habit; do not believe merely on the authority of your teachers and elders. After observation and analysis when it agrees with reason and is conducive to the good and benefit of one and all, then accept it and live upto it."

Yogavasishta also says, that rational investigation is an important step in acquiring knowledge. Rational investigation really aims at realism and it is equally employed in matters other than religion, like physics, metaphysics, psychology and other realms of thought where reasoning is required. It is by employment of reason that people try to understand the nature of God, Truth and Morality. But these three matters have so far eluded their grasp. The nature of God is still in speculation and the standard of truth and morality appear to be relative.

Inspite of this hapless situation rationalism continues its appeal to all those who have cultivated thinking habits and who rebel against the social and religious inequities perpetuated by long habits of restricted thinking. These free thinkers cannot be silent spectators of the inhuman atrocities perpetrated in society in the name of religion and tradition. Can any one subscribe to the inhuman atrocities of torture on nonviolent Jain monks by putting them on spikes by Hindus and torturing Christians by thumb screws, collar of torture and burning them alive by their co-religionists during medieval times? Similarly can any self respecting individual tolerate slavery and bonded labour in society without registering a protest? Free thinking movement is a natural reaction to such atrocities committed by man against man in the name of God and his religion.