Private revelations, which
belong to an undying charism in the Church, have the same nature as public
revelation and the same general purpose of helping the Church. Their object is
either the same as the public revelation, that is, an explanation of the
revealed truths, or something new by which public revelation may be
accidentally extended. It does not, however, identify with public revelation and
does not become an object of faith for others than the person to whom it
is given and who is bound to believe it in by the same supernatural faith, if
he is certain of the revelation by a miraculous sign of God (either exterior or
interior in his mind). If the Magisterium approves such revelations (ass
in the case of St. Margaret Mary Alacoque about the Sacred Heart and t. Bernardette
at Lourdes), one is only obliged to admit their fittingness as approved by the
Church, but he can also, if he chooses, believe them along with the public
revelation, with the same supernatural faith. Such revelations are also useful
for the development of dogma. (Emmanuel Doronzo, The Channels of
Revelation [The Science of Sacred Theology for Teachers 3; Middleburg, Va.:
Notre Dame Institute Press, 1974], 46 n. 50)