All those who would re-enter Paradise must first be tried by fire’, says St Ambrose. Thus the soul which aspires to the earthly Paradise of union with God in contemplation must necessarily be purified, for only the pure of heart can see God. Thus purification both of the senses and of the mind, says Père Garrigou-Lagrange, is caused by a special breathing of the Holy Spirit whose working here becomes manifest in the Gifts of knowledge, Filial Fear and Fortitude for the purification of the senses, and the Gift of Understanding for the purification of the mind.

Knowledge shows experimentally the nothingness of creatures, both within and outside ourselves. It differs from Wisdom in that we see created things in their proximate cause (i.e., failures and imperfections) and not in the Supreme Cause. This Knowledge of the nothingness of created things is meant to lead us to the desire of God alone.

Filial Fear is the Gift which inspires the soul with the fear of being unfaithful, and in spite of the sensitive nature being greatly depressed, weak and sluggish in good works by reason of the lack of attraction, the spirit is ready and strong.