Being a believing Christian is not a moment to moment existential crisis of wondering whether everything we think we believe is really true. Just like most things in life, we spend most of our time functioning as though what we believe is true and proceeding from there. But we still have every right to ask whether it is indeed all true. And we also can ask what exactly of our knowledge is something that can be directly accessible to ourselves rather than founded on the testimony of reliable witnesses.
I ran across a hint at beginning that answer here:
We must at no moment forget that the end of our journey is our meeting with the Risen Christ. Some people, whilst admitting the importance of the Resurrection in the experience of the Apostles, wonder how this apostolic experience can have the same central significance for us; but is it enough for us simply to believe in the words of others and to found our faith on something totally unverifiable? I would like to stress the fact that, of all the historic events in the world, the Resurrection of the Lord belongs equally to past history and to present reality. Christ, dead on the Cross on one particular day, Christ, risen from the tomb in his glorified, human flesh on one particular day, belongs to the past as an historic fact; but Christ, once risen, living forever in the glory of the Father, belongs to the history of each day and each instant, because living, according to his promise, he is with us, now and always. Christian experience from this point of view is essentially attached to the event of the Resurrection, because it is the one event in the Gospels which can become part of our own personal experience. All the rest we receive from tradition, written or spoken — the account of the Crucifixion, the different events told us by Holy Scripture — but the Resurrection, this we know personally, or else we are ignorant of the primordial, essential fact of the Church’s life and the Christian faith. St Symeon the New Theologian said: ‘How can one who knows nothing of the Resurrection in this life, expect to discover and enjoy it in his death?’ Only the experience of the Resurrection and Eternal Life can make the death of the body into sleep and death itself into the Gate of Life.
If such a plain, peremptory statement arouses questions, demands a response, demands of you that you ask yourselves whether you are within Christian experience, so much the better! Here is the central experience without which there are no Christians, there is no Christianity, without which our faith is not faith but credulity; not ‘the certainty of things unseen’ but the capacity to accept the witness of others, an unverifiable witness, a witness which is based on nothing more than that someone has said something which seems incredible but which, nevertheless, for reasons equally incredible, we are prepared to accept.
– Metropolitan Anthony (Bloom) of Sourozh, Meditations on a Theme, pp. 111-113
Metropolitan Anthony goes on to say:
The joy of the Resurrection is something which we, too, must learn to experience, but we can experience it only if we first learn the tragedy of the Cross. To rise again we must die. Die to our hampering selfishness, die to our fears, die to everything which makes the world so narrow, so cold, so poor, so cruel. Die so that our souls may live, may rejoice, may discover the spring of life. If we do this then the Resurrection of Christ will have come down to us also. But without the death on the Cross there is no Resurrection, the Resurrection which is joy, the joy of life recovered, the joy of the life that no-one can take away from us anymore! The joy of a life which is superabundant, which, like a stream runs down the hills, carrying with it heaven itself reflected in its sparkling waters. The Resurrection of Christ is reality in history as his death on the Cross was real, and it is because it belongs to history that we believe in it. It is not only with our hearts but with the totality of our experience that we know the risen Christ. We can know him day after day as the Apostles knew him. Not the Christ of the flesh, not Christ as he was seen in bewilderment by people who surrounded him in the days of his earthly life, but the everliving Christ. The Christ of the spirit of whom St Paul speaks, the risen Christ who belongs to time and eternity because he died once upon the Cross but lives forever. The Resurrection of Christ is the one, the only event that belongs both to the past and to the present. To the past because it did happen, on a given day, in a given place, at a given moment, because it was seen and known as an event in time, in the life of those who had known him. But it belongs also to every day because Christ, once risen, is ever alive, and each of us can know him personally, and unless we know him personally we have not yet learnt what it means to be a Christian (ibid., p. 119, emphasis added).
The whole essay, titled “The Resurrection and the Cross,” is well worth reading (link includes full book text).
I find this explanation of how we can know that the Christian faith is true very well done and not at all given to the fideism on the one hand or condescension on the other that attempts to discuss this subject usually give. And I would also say that I believe an emphasis on the thoroughgoing presence of the resurrection in the life of the Christian is what is often so very absent from many non-Orthodox narratives of spiritual life.
It is one thing to say that one is redeemed or even saved, but there is something much more powerful and complete about understanding spiritual life as truly a resurrection. The resurrection, as Metropolitan Anthony says, reaches into our knowledge that Christianity is true because it is “the one, the only event that belongs both to the past and to the present.”