What is Ivan's transformation in the beginning of Master and Margarita?
Ivan is a struggling poet in the beginning of the novel Master and Margarita. When first shown, he is walking with Berlioz, a famed editor and entrepreneur, and they encounter a strange man who turns out to be the Devil in disguise. The Devil predicts Berlioz's death, and Ivan is stunned but unconvinced, for he is an atheist:
The word "Annushka" quickly led to the words "sunflower oil," and then, for some reason, "Pontius Pilate." The poet rejected Pilate and began to reconstruct the chain... there could not be a shred of doubt that the mysterious consultant had known the exact circumstances of Berlioz's horrific death in advance. Two thoughts pierced the poet's brain. One: "He's no madman! That's nonsense!" and another: "What if he arranged this whole thing himself?"
(Bulgakov, Master and Margarita, Google Books)
This realization, and its implications (although he does not accept the truth at first) is the first step on Ivan's transformation from poet to historian. His nature was to reject the truth even when presented with overwhelming evidence, and so even the tragic event only had a slight effect. However, it opened the door for his eventual "conversion," as he stops writing fictional or symbolic poetry and focuses instead on factual, verifiable history instead.