The Outsider Test for Faith (OTF) is a criterion for rational belief developed by former Christian apologist turned atheist John W. Loftus. Loftus observes that religious affiliation is largely determined by that of one's parents and native country, and to counteract this tendency one should "Test your beliefs as if you were an outsider to the faith you are evaluating." "The best way to test one's adopted religious faith is from the perspective of an outsider with the same level of skepticism used to evaluate other religious faiths." "Tell believers to examine their faith critically and most all of them will say they already do. But tell them to subject their own faith to the same level of skepticism they use when examining the other religious faiths they reject and that will get their attention."
The outsider test codifies a form of argument that has existed in critiques of religion for some time.
Thomas Jefferson in a letter to his nephew Peter Carr, offers some advice on how to study religion:
"In the first place, divest yourself of all bias in favor of novelty & singularity of opinion....You will naturally examine first, the religion of your own country. Read the Bible, then as you would read Livy or Tacitus....In fine, I repeat, you must lay aside all prejudice on both sides, and neither believe nor reject anything, because any other persons, or description of persons, have rejected or believed it. Your own reason is the only oracle given you by heaven, and you are answerable, not for the rightness, but uprightness of the decision."
Robert Ingersoll from his lecture "The Gods" (1872):
"All that is necessary, as it seems to me, to convince any reasonable person that the Bible is simply and purely of human invention -- of barbarian invention -- is to read it. Read it as you would any other book; think of it as you would of any other; get the bandage of reverence from your eyes; drive from your heart the phantom of fear; push from the throne of your brain the coiled form of superstition -- then read the Holy Bible, and you will be amazed that you ever, for one moment, supposed a being of infinite wisdom, goodness and purity, to be the author of such ignorance and of such atrocity."
In Bertrand Russell's speech "Am I An Atheist Or An Agnostic?", Russell said that he could not prove there was no God, but could not disprove the existence of the Homeric gods either. More recently, Richard Dawkins argued "We are all atheists about most of the gods that humanity has ever believed in. Some of us just go one god further."
A similar slogan, coined by Stephen Roberts and used in many internet taglines, says, "I contend we are both atheists, I just believe in one fewer god than you do. When you understand why you dismiss all the other possible gods, you will understand why I dismiss yours."
The basic idea of the outsider test has also been applied to questions more specific than the existence of God. For example Richard Carrier, in an article on Jesus' resurrection, argued "Can you imagine a movement today claiming that a soldier in World War Two rose physically from the dead, but when you asked for proof all they offered you were a mere handful of anonymous religious tracts written in the 1980's? Would it be even remotely reasonable to believe such a thing on so feeble a proof? Well — no."
In his Natural History of Religion, David Hume gives a long discussion of how the beliefs of one religion may appear absurd to another, though he draws no explicit conclusions from this fact. Included in this discussion is an imagined exchange between a Catholic and a pagan:
- "How can you worship leeks and onions? we shall suppose a SORBONNIST to say to a priest of SAIS. If we worship them, replies the latter; at least, we do not, at the same time, eat them.* But what strange objects of adoration are cats and monkies? says the learned doctor. They are at least as good as the relics or rotten bones of martyrs, answers his no less learned antagonist. Are you not mad, insists the Catholic, to cut one another's throat about the preference of a cabbage or a cucumber? Yes, says the pagan; I allow it, if you will confess, that those are still madder, who fight about the preference among volumes of sophistry, ten thousand of which are not equal in value to one cabbage or cucumber."
- Loftus, John W. Why I Rejected Christianity: A Former Apologist Explains 1st Edition (Trafford 2006).
- Loftus, John W. Why I Became an Atheist: A Former Preacher Rejects Christianity (Prometheus Books, 2008).
- Loftus, John W. ed. The Christian Delusion: Why Faith Fails (Prometheus Books, 2010).
- Loftus, John W. ed. The End of Christianity (Prometheus Books, 2011)