1 Corinthians 15:14: "And if Christ be not risen, then is our preaching vain, and your faith is also vain." (KJV)
Ludwig Wittgenstein, Culture and Value, U. of Chicago Press, 1980, tr. Peter Winch, p. 32e, entry from 1937:
Queer as it sounds: The historical accounts in the Gospels might, historically speaking, be demonstrably false and yet belief would lose nothing by this: not, however because it concerns 'universal truths of reason'! Rather because historical proof (the historical proof-game) is irrelevant to belief. This message (the Gospels) is seized on by men believingly (i.e. lovingly). That is the certainty characterizing this particular acceptance-as-true, not something else.
A believer's relation to these narratives is neither the relation to historical truth (probability), nor yet that to a theory consisting of 'truths of reason'. [ . . .]
Central to the Gospel accounts is that Christ was seen alive by numerous witnesses after his crucifixion and death. Assuming that 'faith' and 'belief' are interchangeable in this context, Paul is saying that belief in Christ as savior is vain (empty, without substance) if the Gospel accounts are false. Wittgenstein, however, is maintaining the exact opposite: Christian belief loses nothing of its substance even if the Gospel accounts could be proven to be false.
How can Wittgenstein maintain something so seemingly preposterous?
Christianity is a form of life, a language-game, self-contained, incommensurable with other language-games, under no threat from them, and to that extent insulated from logical, historical, and scientific objections, as well as from objections emanating from competing religious language-games.
This is why the "historical proof-game" is irrelevant to Christian belief. The two language games are not in competition.
But is the Christian belief system true? Evasion of this question strikes me as impossible.
Here is where the Wittgensteinian approach stops making sense for me. No doubt a religion practiced is a form of life; but is it a reality-based form of life? When Jesus told Pontius Pilate that he had come into the world to bear witness to the truth, Pilate dismissed his claim with the skeptical, "What is truth?" I for one cannot likewise dismiss the question of the truth of Christianity in Pilate's world-weary way. (Pilate comes across to me like a Pyrrhonian skeptic who is tired of these deep questions and just doesn't care any more.) If Christianity is true, it is objectively true; it corresponds to the way things are; it is not merely a set of beliefs that a certain group of people internalize and live by, but has an objective reference beyond itself.
And no doubt religions can be usefully viewed as language games. But Schachspiel is also a Sprachspiel. What then is the difference between Christianity and chess? Chess does not, and does not purport to, refer to anything beyond itself. Christianity does so purport. This is why it is absurd when L. W claims, in other places, that Christianity is not a doctrine. Of course it is a doctrine. Its being much more than a doctrine does not show otherwise.
So I say the following. If it is demonstrable that the Resurrection did not occur, then Christian faith is in vain. Paul is right and Ludwig is wrong. Historical investigation cannot be wholly irrelevant to Christian belief. On the other hand, at some point one has to make a faith commitment. This involves a doxastic leap since one cannot prove that the Resurrection did occur. Will is superadded to intellect and one decides to believe. It may help to reflect that unbelief is also a decision and also involves a leap. Given the infirmity of reason, and the welter of conflicting considerations, it is impossible to know which leap is more likely to be a leap onto solid ground.
"Go on, believe! It does no harm." (CV, 45e)
Existentially, this may well be the decisive consideration. What, after all, does the believer lose if Christianity turns out to be false? Where is the harm in believing? On the other hand, should it prove to be true . . . .
So while Wittgenstein, like Kierkegaard, takes an extreme, and ultimately untenable view, he has existential insights that need accommodation.
Here is an extended post on Wittgensteinian fideism.