Believe what? To believe blindly is to degenerate the human soul. Be an atheist if you want, but do not believe in anything unquestioningly. Why degrade the soul to the level of animals? You not only hurt yourselves thereby, but you injure society, and make danger for those that come after you. Stand up and reason out, having no blind faith. Religion is a question of being and becoming, not of believing. This is religion, and when you have attained to that you have religion. Before that you are no better than the animals. "Do not believe in what you have heard," says the great Buddha, "do not believe in doctrines because they have been handed down to you through generations; do not believe in anything because it is followed blindly by many; do not believe because some old sage makes a statement; do not believe in truths to which you have become attached by habit; do not believe merely on the authority of your teachers and elders. Have deliberation and analyse, and when the result agrees with reason and conduces to the good of one and all, accept it and live up to it."
- Swami Vivekananda
The Complete Works of Swami Vivekananda/Volume 4/Lectures and Discourses/The Claims of Religion