AC 9780 - How can we know what good is?

AC 9780
. . . the Word is the doctrine of good,
because it is the doctrine of love to the Lord
and of love toward the neighbor;
and all good is of love, even the good of faith,
for this comes forth from the good of love, and not without it.

[2] As the Word is the doctrine of good,
therefore in order that the Word may be understood,
it must be known what good is;
and no one knows what good is
unless he lives in good according to the Word;
for when anyone lives in good according to the Word,
then the Lord instills good into his life,
from which the person perceives it and feels it,
and consequently apprehends the nature of it;
otherwise it does not appear, because it is not perceived.