This book contains the substance of courses of lectures given at Cambridge in 1913-14 to classes consisting chie?y of candidates for the ministry of the Church of England. There are few questions of more practical impor tance to Christian people, whether clergy or laity, than those which are raised by a study of the character, the work, and the functions of the Catholic Church. Upon the answer which we give to those questions depends our attitude, as individuals, towards the great society of which we are members. It determines for each of us whether he shall march in the war against sin and unbelief as a soldier in the army of Christ, under the command of its officers, conscious of the honour and the joy of serving in the ranks of a trained and disciplined force; or as an irresponsible adventurer, brave and loyal at heart, but a member of an irregular company, which follows no leaders but such as are chosen by itself.