Why I am Not a Christian

As your chairman has told you, the subject about which I am going to speak to you tonight is "Why I Am Not a Christian." Perhaps it would be as well, first of all, to try to make out what one means by the word "Christian." It is used in these days in a very loose sense by a great many people. Some people mean no more by it than a person who attempts to live a good life. In that sense I suppose there would be Christians in all sects and creeds; but I do not think that that is the proper sense of the word, if only because it would imply that all the people who are not Christians -- all the Buddhists, Confucians, Mohammedans, and so on -- are not trying to live a good life. I do not mean by a Christian any person who tries to live decently according to his lights. I think that you must have a certain amount of definite belief before you have a right to call yourself a Christian. The word does not have quite such a full-blooded meaning now as it had in the times of St. Augustine and St. Thomas Aquinas. In those days, if a man said that he was a Christian it was known what he meant. You accepted a whole collection of creeds which were set out with great precision, and every single syllable of those creeds you believed with the whole strength of your convictions.

Link