The book is a series of independent demonstrations, the results of which accumulate to the final conclusion, that the Christian religion is necessarily the only religion possible to meet the spiritual wants of mankind. In arriving at this conclusion, the different arts and processes of revealed religion are examined, and their adaptedness to perform their several functions in elevating, purifying, and actuating the human soul to benevolent effort, is determined, and, finally, the practical operation of the system is shown, as a matter of undeniable experience, to produce the complete and necessary result required. . . . As four is contained in twelve three times, and as twelve is the only number in which four is three times contained; so the capacities and susceptibilities of the human soul being given, and the power and adaptations of revelation being ascertained, the result is obtained (may it not be said with mathematical certainty?) that Christianity, as taught by the interpretation and experience of evangelical Christians, is the true religion and the only religion possible for human nature. (Introduction from Preface to 2nd Edition.)