— Gospel of Matthew 16:1–4
'And a great portent appeared in heaven, a woman clothed with the sun, with the moon under her feet, and on her head a crown of twelve stars.'
— Book of Revelation 12:1
In his 2014 book Hvorfor skriver ikke Gud på himmelen? [Why Doesn't God Write in the Sky?], the Norwegian theologian and philosopher Espen Ottosen deals with the difficult question of God's 'hiddenness': If there really is a God, why doesn't He make His own existence more obvious, so that everyone becomes convinced and starts to believe in Him? Ottosen tells a story about Inge, a Christian Scout leader who made a strong impression on him as a young boy. One night they were talking, Inge said: 'Why doesn't God write in the sky that He exists?' 
Ottosen writes that, according to the Bible, God already has written in the sky – at least 'in one sense'  – namely, when the sun stood still over a battle in the Book of Joshua: 'The sun stayed in the midst of heaven, and did not hasten to go down for about a whole day' (Joshua 10:13). This made me think of the so-called 'Miracle of the Sun' which, according to the Catholic Church, took place at Fátima in 1917. I would like to suggest that this miracle was in fact a sign from heaven, and perhaps one of the closest things we have to a visible proof of God's existence.
Ottosen writes that he is 'a doubting man', and that he therefore has 'an abundant need to defend my faith – both to myself and to others.'  He says that he has read several of the books written by the 'New Atheists' – including Richard Dawkins, Christopher Hitchens, and Sam Harris – with great interest, and that he takes their objections to Christianity seriously: 'To me, it is a question of [intellectual] honesty. If there are no good answers – indeed, if the atheists and skeptics are actually right – there is little else to do but to give up the faith.'  I appreciate this attitude.
Fortunately, there are good responses to atheistic objections – and good arguments for God's existence. Ottosen presents several of these, and shows that he has knowledge of authors from C.S. Lewis to William Lane Craig, Alvin Plantinga, Alister McGrath, John Lennox, Richard Swinburne, Keith Ward, Edward Feser and several others that are well known in the world of Christian apologetics. However, the most important objection he addresses in the book is that 'God often appears to be somewhat silent and passive.'  Why aren't there more miracles in response to prayers?
Ottosen writes about so-called dispensationalists, Christians who believe that God's miraculous intervention in the world is no longer necessary – and therefore does not take place. The argument goes like this: 'Before the Bible existed, God wanted to substantiate the message of the early Christians with powerful signs and wonders. But today, we have the Bible.'  Ottosen acknowledges that this may explain why God is perceived as hidden, but it does nothing to help those who actually experience this hiddenness: 'For what shall I say to those who beg and ask God to intervene with a powerful miracle? I have met people who have read a lot in the Bible, but who are still not convinced that they have thereby encountered God.' 
As is well known, the Catholic Church does not believe in the principle of 'Scripture alone' (Sola Scriptura), that is, that the Bible itself is enough. The Bible is read in light of Tradition, and in the context of a living Church which unites every Sunday to worship God together. In every Mass, a real miracle takes place: the essence of bread and wine is transformed into the body and blood, soul and divinity of Jesus Christ through transubstantiation. But the Catholic Church also contains a treasure trove of many more miracles – signs that confirm the Gospel (cf. Mark 16:20) – which, unfortunately, are not talked about as often. One of these is the Miracle of the Sun at Fátima.
On 13 May 1917, three shepherd children – Lúcia dos Santos and her younger cousins, Francisco and Jacinta Marto – were out herding sheep in an area known as the Cova da Iria near Fátima in Portugal. The Catholic historian William Thomas Walsh (1891–1949), who wrote the book Our Lady of Fátima based on eyewitness accounts from Lúcia and others involved, writes that the three children 'were startled by a flash so brilliant that they took it to be lightning.' Suddenly, there stood before them 'a Lady all of white, more brilliant than the sun dispensing light, clearer and more intense than a crystal cup full of crystalline water penetrated by the rays of the most glaring sun.' 
When the children asked where the lady came from, she replied: 'I am from heaven', and she asked them to pray five decades of the Rosary every day – so that God would put an end to the First World War, which was raging at this time.  She gave them an important message: 'Jesus wishes to make use of you to have me acknowledged and loved. He wishes to establish in the world the devotion to my Immaculate Heart.' She also asked them to return to the same place on the 13th day of each month, until October: 'In October I will tell you who I am and what I wish, and will perform a miracle that everyone will have to believe.' 
Although the children did not realise it from the beginning, it became clear that the Lady was the Virgin Mary. She had revealed herself to these children, just as she had revealed herself to St. Juan Diego in Mexico in 1531, and to St. Bernadette Soubirous in Lourdes in 1858. The Catholic Church recognises several such 'Marian apparitions' as credible, and many of them have led to miracles in addition to the apparition itself – such as the healing of illnesses. At Fátima, Mary also gave three prophetic warnings (or 'secrets') about events that would happen in the near future: the spread of Communist ideology from Russia, a new and even worse war after the one that ended in 1918, etc. As we know, these prophecies came true.
The day finally came, 13 October. The children had told everyone they knew about the fact that the Virgin had appeared to them, and as many as 70,000 men, women, and children had turned up to witness the promised miracle. It was raining heavily, and several in the crowd had soaking wet clothes. Finally, it stopped raining, and 'something stupendous, unheard of, almost apocalyptic' happened in the sky. Walsh describes it as follows:
The sun stood forth in the clear zenith like a great silver disk which, though bright as any sun they had ever seen, they could look straight at without blinking, and with a unique and delightful satisfaction. This lasted but a moment. While they gazed, the huge ball began to "dance"—that was the word all the beholders applied to it. Now it was whirling rapidly like a gigantic fire-wheel. After doing this for some time, it stopped. Then it rotated again, with dizzy speed. Finally there appeared on the rim a border of crimson, which flung across the sky red streamers of flame, reflecting to the earth, to the trees and shrubs, to the upturned faces and the clothes all sorts of brilliant colors in succession: green, red, orange, blue, violet, the whole spectrum in fact. Madly gyrating in this manner three times, the fiery orb seemed to tremble, to shudder, and then to plunge precipitately, in a mighty zigzag, toward the crowd. The spectators were not harmed by the sun falling towards them, but several people later said that it suddenly became much warmer. The whole miracle lasted for about ten minutes, before the sun climbed back up to its natural place in the sky. Those who had previously had wet clothes and umbrellas now discovered that they had dried up.  Theories suggesting that the experience of the crowd of 70,000 was due to some form of hypnosis or mass hallucination were rejected when it became known that credible eyewitnesses had seen the miracle from several miles away,  and the Miracle of the Sun was taken as evidence that the children were speaking the truth about the Lady who had revealed herself to them in the Cova da Iria.
We can easily understand why Mary would say that 'everyone will have to believe' this miracle. Would there have been any doubt in our minds that this was a genuine miracle if we had been there that day? Well, it depends. Ottosen points out that although Jesus proved who He was through signs and wonders, many people did not believe in Him because they simply did not want to believe: 'When Jesus had said this, He departed and hid Himself from them. Though He had done so many signs before them, yet they did not believe in Him' (John 12:36–37). 'Thus, it might not be so certain that God would gain very much from writing in the sky that He exists', Ottosen writes, for it is 'not at all certain that the result would have been an increase of Christian belief.' 
A confirmation of this suspicion is found in the fact that not everyone who witnessed the Miracle of the Sun at Fátima became Christians. It may seem like a conspiracy theory, but Catholic countries have a long history of very aggressive and sometimes violent opposition to the Church from radical and anti-clerical liberals, Freemasons and secret societies, such as the 'Carbonari'. This led to armed conflict in France, Italy, Mexico – and in Portugal. Following a revolutionary coup in 1910, a republican government was set up that was hostile to the Catholic Church. The same was true of Arturo de Oliveira Santos, who was the mayor of Ourém – the Portuguese municipality wherein Fátima is located. Walsh writes:
At twenty-six he joined the Grand Orient Lodge at Leiria, [...] He became indoctrinated wih the esoteric lore of a syncretistic and naturalistic religion which had been the chief opponent of the Catholic Church in modern times, and which already boasted that, by planning and carrying out the Portuguese revolution of 1910, it had taken a long step toward the total elimination of Christianity in the Iberian Peninsula. Avelino de Almeido, who was the editor of O Século – one of the biggest newspapers in Lisbon at the time – was also 'a Freemason who made no secret of his dislike for priests, sacraments, creeds and dogmas.'  It should not surprise us that neither Almeido nor Oliveira Santos converted to Christianity as a result of the miracle, although O Século – as well as other anti-clerical newspapers in Portugal – was forced to report that it had actually taken place. Oliveira Santos denied that there was anything miraculous about the incident, and 'he would have denied it even if he had been there.'  Walsh rightly compares him to the Pharisees who denied the resurrection of Christ, even after witnessing the death of Jesus on the cross.
The latter is a point that Ottosen also makes. Jesus told the Pharisees, who wanted a sign from heaven, that they were to receive 'the sign of Jonah', i.e. His own death and resurrection on the third day. 'Jesus clearly thinks this is sufficient', Ottosen writes. 'If saving faith is more than a thoughtful conviction – if it is also about loving God and wanting to do His will – it is not certain that an extra miracle will make someone a Christian.'  For those who sincerely seek God and want to believe, the resurrection is sufficient; for those who do not want to believe, nothing is sufficient. This is one of the most important conclusions Ottosen draws in his book.
It is possible that God doesn't perform more miracles or appear to those who do not believe in Him, because it wouldn't change anything. After Jesus was rejected in His own hometown, we read that 'He did not do many mighty works there, because of their unbelief' (Matthew 13:58). In this context, Ottosen quotes the American philosopher Paul K. Moser, who believes that God will not reveal His existence to those who do not want a personal relationship with Him: 'It is obvious that God would not be obligated to reveal Himself to proud people who perceive themselves as intellectually exalted and who resolutely and firmly oppose God's way of doing things.'  Such were the mayor of Ourém and the editor of O Século.
But the three shepherd children at Fátima, and the humble peasants who made up a large part of the crowd who witnessed the Miracle of the Sun in 1917, were something else entirely. In the preface to his book, Walsh asks why the Virgin Mary would choose to appear in the Portuguese countryside, of all places. His answer goes like this:
Well, first of all she appears where it pleases God, and her. But the Portuguese have an idea that they were favored partly, at least, because their country has always been called a terra de Santa Maria; and in the Serra about Fátima, regardless of revolutions and apostacies in other places, the poor have clung for centuries with unwavering devotion to the recitation of her Rosary. Ottosen also quotes the French philosopher Blaise Pascal (1623–1662), who wrote that God 'hides from those who tempt Him, and reveals Himself to those who seek Him'. In other words, God is 'so disguised that He will only be perceived by those who seek Him with all their heart'.  The Lord says to the people of Israel: 'You will seek me and find me; when you seek me with all your heart, I will be found by you' (Jeremiah 29:13-14).
In order for us to find God – not only in magnificent wonders like the Miracle of the Sun at Fátima, but in the 'still small voice' (1 Kings 19:12) that the noise of the world can so easily overpower – we must seek Him with a whole heart. In this we can look to the Virgin Mary, the one who revealed herself to three shepherd children in Portugal, as our greatest role model. When some very different shepherds came to the manger in Bethlehem, to worship the baby that Mary had given birth to that night, we read that she 'kept all these things, pondering them in her heart' (Luke 2:19). And on 13 July 1917, at Fátima, she said: 'In the end my Immaculate Heart will triumph.' 
 Ottosen, Espen. Hvorfor skriver ikke Gud på himmelen? Litt om min tvil. Mest om min tro, 9. Oslo: Lunde Forlag, 2014. All translations are mine.
 Ibid., 20.
 Ottosen, Hvorfor skriver ikke Gud på himmelen?, 11.
 Ibid., 13.
 Ibid., 64.
 Ibid., 23.
 Ibid., 24.
 Walsh, William Thomas. Our Lady of Fátima, 50. New York, NY: Image Books, 1954.
 Ibid., 51 & 52.
 Ibid., 68 & 80.
 Ibid., 145–146.
 Ibid., 146–147.
 Ibid., 148–149.
 Ottosen, Hvorfor skriver ikke Gud på himmelen?, 192.
 Walsh, Our Lady of Fátima, 95–96.
 Ibid., 139.
 Ibid., 150
 Ottosen, Hvorfor skriver ikke Gud på himmelen?, 209.
 Quoted in Ottosen, Hvorfor skriver ikke Gud på himmelen?, 211–212.
 Walsh, Our Lady of Fátima, Preface.
 Quoted in Ottosen, Hvorfor skriver ikke Gud på himmelen?, 220.
 Walsh, Our Lady of Fátima, 82.