ished according to
the various errors that occur in matters of faith, there are not
determinate species of unbelief: for errors can be multiplied
indefinitely, as Augustine observes (De Haeresibus).

Reply Obj. 1: The formal aspect of a sin can be considered in two
ways. First, according to the intention of the sinner, in which case
the thing to which the sinner turns is the formal object of his sin,
and determines the various species of that sin. Secondly, it may be
considered as an evil, and in this case the good which is forsaken is
the formal object of the sin; which however does not derive its
species from this point of view, in fact it is a privation. We must
therefore reply that the object of unbelief is the First Truth
considered as that which unbelief forsakes, but its formal aspect,
considered as that to which unbelief turns, is the false opinion that
it follows: and it is from this point of view that unbelief derives
its various species. Hence, even as charity is one, because it
adheres to the Sovereign Good, while there are various species of
vice opposed to charity, which turn away from the Sovereign Good by
turning to various temporal goods, and also in respect of various
inordinate relations to God, so too, faith is one virtue through
adhering to the one First Truth, yet there are many species of
unbelief, because unbelievers follow many false opinions.

Reply Obj. 2: This argument considers the various species of unbelief
according to various points in which errors occur.

Reply Obj. 3: Since faith is one because it believes in many things
in relation to one, so may unbelief, although it errs in many things,
be one in so far as all those things are related to one. Yet nothing
hinders one man from erring in various species of unbelief, even as
one man may be subject to various vices, and to various bodily
diseases.
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SIXTH ARTICLE [II-II, Q. 10, Art. 6]

Whether the Unbelief of Pagans or Heathens Is Graver Than Other Kinds?

Objection 1: It would seem that the unbelief of heathens or pagans is
graver than other kinds. For just as bodily disease is graver
according as it endangers the health of a more important member of
the body, so does sin appear to be graver, according as it is opposed
to that which holds a more important place in virtue. Now that which
is most important in faith, is belief in the unity of God, from which
the heathens deviate by believing in many gods. Th