Author's purpose was to present a clear and precise substance of Catholic doctrine and its basis in the sources of revelation. Ordained as teaching material, and not to exceed the margin of a manual, only presented in each subject's most significant statements magisterium, some biblical texts and patristic some text. For the sake of brevity, always tried to give preference to the positive test on the speculation. The bibliography consists of a selection of the most outstanding in the field. Successive editions of the Spanish version made ​​are evidence of the acceptance of this text book.