John H. Stapleton,
Explanation of Catholic Morals
“ An apostate is one who, having once believed, ceases to believe. All heretics and infidels are not apostates, although they may be in themselves or in their ancestors. One may apostatize to heresy by rejecting the Church, or to infidelity by rejecting all revelation; a Protestant may thus become an apostate from faith as well as a Catholic. This going back on the Almighty—for that is what apostasy is,—is, of all misfortunes the worst that can befall man. There may be excuses, mitigating circumstances, for our greatest sins, but here it is useless to seek for any. God gives faith. ”
