Of the seven sacraments it will be noticed that two--baptism and penance--dealt with the forgiveness of sins, and that two--holy orders and matrimony--were received only by certain persons. Three--baptism, confirmation, and holy orders--could be received by a Christian only once. Two--confirmation and holy orders--required the ministry of a bishop; and all others, except baptism and possibly matrimony, required the ministry of at least a priest. The priesthood was, therefore, the absolutely indispensable agent of the Church in the administration of the sacramental system. It was the priesthood that absolved penitents from their sins, wrought the great daily miracle of transubstantiation, and offered to God the holy sacrifice of the Mass. [Sidenote: Various Objections to the Church] It must not be supposed that either the theology or the organization of the Catholic Church, as they existed in the year 1500, had been precisely the same throughout the Christian era. While educated Catholics insisted that Christ was indirectly the source of all faith and all practice, they were quite willing to admit that external changes and adaptations of institutions to varying conditions had taken place. Moreover, it must not be supposed that the proud eminence to which the Catholic Church had attained by 1500 in central and western Europe had been won easily or at that time was readily maintained. Throughout the whole course of Christian history there had been repeated objections to new definitions of dogma--many positively refused to accept the teaching of the Church as divine or infallible-- and there had been likewise a good deal of opposition to the temporal claims of the Church, resulting in increasing friction between the clergy and the lay rulers. Thus it often transpired that the kings who vied with one another in recognizing the spiritual and religious headship of the pope and in burning heretics who denied doctrines of the Catholic Church, were the very kings who quarreled with the pope concerning the latter's civil jurisdiction and directed harsh laws against its exercise. [Sidenote: Sources of Conflict between Church and State]