If you have seen a certain country, and a man forces you to say that you have not seen it, still in your heart of hearts you know you have. So, when you see religion and God in a more intense sense than you see this external world, nothing will be able to shake your belief. Then you have real faith. That is what is meant by the words in your Gospel, "He who has faith even as a grain of mustard seed." Then you will know the Truth because you have become the Truth.