unbelief, which does not seem to agree with what has been said
(Q. 10, A. 5). Therefore apostasy does not pertain to unbelief.

_On the contrary,_ It is written (John 6:67): "Many of his disciples
went back," i.e. apostatized, of whom Our Lord had said previously
(John 6:65): "There are some of you that believe not." Therefore
apostasy pertains to unbelief.

_I answer that,_ Apostasy denotes a backsliding from God. This may
happen in various ways according to the different kinds of union
between man and God. For, in the first place, man is united to God by
faith; secondly, by having his will duly submissive in obeying His
commandments; thirdly, by certain special things pertaining to
supererogation such as the religious life, the clerical state, or
Holy Orders. Now if that which follows be removed, that which
precedes, remains, but the converse does not hold. Accordingly a man
may apostatize from God, by withdrawing from the religious life to
which he was bound by profession, or from the Holy Order which he
had received: and this is called "apostasy from religious life" or
"Orders." A man may also apostatize from God, by rebelling in his
mind against the Divine commandments: and though man may apostatize
in both the above ways, he may still remain united to God by faith.

But if he give up the faith, then he seems to turn away from God
altogether: and consequently, apostasy simply and absolutely is that
whereby a man withdraws from the faith, and is called "apostasy of
perfidy." In this way apostasy, simply so called, pertains to
unbelief.

Reply Obj. 1: This objection refers to the second kind of apostasy,
which denotes an act of the will in rebellion against God's
commandments, an act that is to be found in every mortal sin.

Reply Obj. 2: It belongs to faith not only that the heart should
believe, but also that external words and deeds should bear witness
to the inward faith, for confession is an act of faith. In this way
too, certain external words or deeds pertain to unbelief, in so far
as they are signs of unbelief, even as a sign of health is said
itself to be healthy. Now although the authority quoted may be
understood as referring to every kind of apostate, yet it applies
most truly to an apostate from the faith. For since faith is the
first foundation of things to be hoped for, and since, without faith
it is "impossible to please God"; when once faith is removed, man
retains nothing that may be useful fo