In all my life I have met only one person who claims to have seen a ghost. And the interesting thing about the story is that that person disbelieved in the immortal soul before she saw the ghost and still disbelieves after seeing it. She says that what she saw must have been an illusion or a trick of the nerves. And obviously she may be right. Seeing is not believing.
For this reason, the question whether miracles occur can never be answered simply by experience. Every event which might claim to be a miracle is, in the last resort, something presented to our senses, something seen, heard, touched, smelled, or tasted. And our senses are not infallible. If anything extraordinary seems to have happened, we can always say that we have been the victims of an illusion. If we hold a philosophy which excludes the supernatural, this is what we always shall say. What we learn from experience depends on the kind of philosophy we bring to experience. It is therefore useless to appeal to experience before we have settled, as well as we can, the philosophical question.
This is quote is a fascinating extension of the argument I make in Hunting Magic Eels, that faith flows from practices of attention. Faith is an act of perception.
Lewis' point here is that perception is inherently theological. Vision is philosophical. Seeing is a practice of metaphysics.
