Whether apostasy pertains to unbelief?

❌ Objection 1 : It would seem that apostasy does not pertain to unbelief. For that which is the origin of all sins, does not, seemingly, pertain to unbelief, since many sins there are without unbelief. Now apostasy seems to be the origin of every sin, for it is written (Ecclus. 10:14): "The beginning of the pride of man is apostasy [Douay: 'to fall off'] from God," and further on, (Ecclus. 10:15): "Pride is the beginning of all sin." Therefore apostasy does not pertain to unbelief.

❌ Objection 2 : Further, unbelief is an act of the understanding: whereas apostasy seems rather to consist in some outward deed or utterance, or even in some inward act of the will, for it is written (Prov. 6:12-14): "A man that is an apostate, an unprofitable man walketh with a perverse mouth. He winketh with the eyes, presseth with the foot, speaketh with the finger. With a wicked heart he deviseth evil, and at all times he soweth discord." Moreover if anyone were to have himself circumcised, or to worship at the tomb of Mahomet, he would be deemed an apostate. Therefore apostasy does not pertain to unbelief.

❌ Objection 3 : Further, heresy, since it pertains to unbelief, is a determinate species of unbelief. If then, apostasy pertained to unbelief, it would follow that it is a determinate species of unbelief, which does not seem to agree with what has been said (Question [10], Article [5]). Therefore apostasy does not pertain to unbelief.