
Yes, there are these two senses of interpretation, and certainly our
decision to accept Scripture as inspired ultimately rests on our own
private opinion.  However, when reading Scripture, we have to remember
that the Scriptures were given by God for our instruction, and that
the interpretation that matters is the one God intended.  For example,
if I decide that the fact that John the Baptist is Elijah teaches the
doctrine of reincarnation, I am wrong because that is not the intended
interpretation.  The prophets didn't make up this teaching; it came
from God, and we must accept it as such.  This necessarily means that
our private interpretations must take a back seat to the meaning God
intended to convey.  Certainly we must rely on our best efforts to
determine what this meaning is, but this very fact should make us
recognize that our private interpretations cannot be automatically
accepted as the infallible interpretation of God.  We need to test the
spirits to see if they are from God.  When the Holy Spirit speaks, he
says the same thing to all; he won't tell me that a passage means one
thing and tell you it means another.  If the two of us come to
conflicting conclusions, we can't both be completely right.  We know
our interpretations are reliable only when the Church as a whole
agrees on what Scripture means.  This is how we know the doctrines of
the Trinity, the dual nature of Christ, etc. infallibly.  These
matters are not up for private interpretation.

This is the reason Peter goes on to talk about the deceptiveness of
the false teachers.  They preferred their own private interpretation
to the God-given teaching of the apostles.  It is through such private
interpretation that the traditions of men, so soundly denounced in
Scripture, are started.