That he did go wrong seems obvious - in that his life was intensely sad, angry and pessimistic and he was more tormented by religion than helped - such that his 'last words' "Tell them I've had a wonderful life" seemed astonishing and incommensurable to those who knew him best.
And where he went wrong is not far to seek.
(From Culture and Value page 53)
One of the things Christianity says, I think, is that all sound doctrines are of no avail. One must change one's life. (Or the direction of one's life.)
The first sentence is false - but characteristic. Wittgenstein rejected 'doctrine' and he rejected any 'cosmology' or story or description of the nature of God and reality and Man's relationship and purpose in relation to God and reality - and any account of the specific implications of this description.
But it is - surely - very obviously untrue that these things don't matter to Christianity; at least, it is very hard to think of a Christian exemplar who did not have a belief in doctrine and an understanding of what life is about.
Indeed these things are absolutely essential to any minimally-coherent 'good life'. Wittgenstein placed enormous emphasis on 'good works', on 'helping others'- acts of kindness, altruism, alleviating suffering - but none of this can be done without a prior knowledge of what life is about.
If you do not know what 'good' is, then how could you know you were doing good to others?
Because if you don't know what life is about, then how can you 'help' anybody? You do not even know what 'help' is.
(Not even so minimalist and apparently-uncontroversial a principle as 'alleviation of human suffering' is adequate as a guide for 'doing good' - since this also implies a program for humanely-killing those who suffer now, or fear suffering in the future; and the need for more of his kind of thing is indeed a major theme of modern public discourse on 'euthanasia'. There is always a need to conceptualize suffering in a context of purpose, meaning, principles etc.)
Instinct or doing what seems natural is no assistance, because there are several or many goods, which conflict and clash - and must be prioritized and integrated.
Wittgenstein wanted faith and a New Life, but without believing the truth of anything in particular - hence he insisted on Christianity as a pure, inexplicable and ungrounded psychological change coming upon a person.
But this is grossly incomplete as an account of any actual or long-term-viable Christianity - or, at least, it takes for granted a vast implicit social-cultural grounding.
As it stands, Wittgenstein's account of Christianity sans cosmology, sans doctrine cannot be prevented from toppling-over-into relativism and subjectivism - hence nihilistic nonsense. And this has been Wittgenstein's major philosophical legacy.
The interesting question is why Wittgenstein made such an obvious and gross blunder - did he really not perceive the inadequacy of his assertions? Surely his own life (and the lives of people around him - many of whom were exemplars of hyper-intelligent glib shallowness and self-indulgence) refuted his expressed views?
Or was it a psychological blind spot - something Wittgenstein personally could not do, so he assumed it was a universal incapacity?
Or was there a valid reason - such that Wittgenstein simply could not commit himself fully to Christian doctrines and cosmology as he knew them? I suspect that this was the real answer. For example, he expressed profound reservations about Predestination, and seemed very averse to scholastic philosophy in Roman Catholicism - probably there were others.
The way I suppose it worked was something like the following: Wittgenstein could not accept the validity of Predestination as he understood it; and while he accepted that there may be a higher sense in which it was true - he could not simply take that on trust when it was insisted that he believe, make public avowal of the truth of, predestination here and now.
(Such a declaration would be required before Wittgenstein would be qualified and entitled to become a church member of some (Calvinistic?) Protestant denominations, which he presumably felt otherwise attracted towards.)
Something similar probably applied to the necessity for acknowledging the ultimate validity of the philosophical system of Thomism (including Aquinas's proofs of the existence of God, which W particularly objected-to) within the Roman Catholic church.
Since Wittgenstein could not with honesty swear to the truth and validity of certain core doctrines or philosophical propositions, regarded as essential for all members, there was simply no possibility of Wittgenstein becoming a church member in any of the denominations of which he knew.
Yet he quite possibly regarded church membership as essential to the status of being a publicly-identified Christian. So he was stuck - outside of any actual denomination, yet extremely concerned with Christianity: 'merely' a simple believer in the reality of Christianity in his own life, and the lives of others.
So Wittgenstein reduced the definition of Christianity to being something inferred from 'the difference it makes to a person's life' - which is correct but incomplete.
In trying to make sense of his (chronic, painful) situation; Wittgenstein tried to argue that doctrines were not a necessary part of Christianity, since it was doctrines which kept him out of the churches.
In a limited sense, then, this hostility to Christian doctrine was an accurate specific observation - Wittgenstein himself was a Christian despite being unable publicly to assent to some specific doctrines variously regarded as crucial to church membership by the known Christian denominations - but as a general principle the hostility to Christian doctrine, and statements that Christianity did not require doctrine, was false: an error.
