We do not have a complete and satisfying knowledge of the world. We are reduced to the simple conclusion that everywhere in the world there is life like ourselves and that all life is shrouded in mystery. A true acquaintance with the world consists in being filled with a sense of the mystery of existence and life. This mystery becomes only more mysterious with every advance in scientific research. To be filled with the mystery of life is like that which is called in the language of mysticism the "wise ignorance," an ignorance which is nonetheless knowledge of the essential.