In the book, Ivan's argument is that there is no justice in the world. He is very unhappy with the suffering of people on earth, and says: "I must have retribution (justice), or I will destroy myself. And not retribution in some remote (far away) infinite time and space, but here on earth, and that I could see myself." But there "is" no absolute justice in the world. So, Ivan says that there are only two things that can be true: either God is not real, or if He is real, He must be an unjust and unwise God.