Why Four Gospels?

From the foreword: "We are fully assured that there is very much in the four Gospels which manifest the Divine perfections and distinctive beauties of each one, which has not yet been brought forth by those who have sought to explore their inexhaustible depths; that there is here a wide field for diligent research, and that those who will pursue this study, prayerfully, for themselves, will be richly rewarded for their pains."