Men who are leading a spiritual life see by the eyes of their heart how the devil lays his snares, how the angels guide us, and how the Lord, in His Sovereign power, allows the temptations, and how he comforts.
Before the writing of the Holy Scriptures, that is, of the sacred texts of the Gospels, the Acts and the Epistles of the Apostles, and before they were spread to the churches of the world, the church was based on Sacred Tradition....The holy texts are in relation to Sacred Tradition what the part is to the whole.
Of the beliefs and public doctrines entrusted to the care of the Church, there are some which are based on Scriptural teaching, others which we have received handed down in mystery by the tradition of the Apostles; and in relation to the true religion they both have the same force.
Our holy fathers have renounced all other spiritual work and concentrated wholly on this one doing, that is, on guarding the heart, convinced that, through this practice, they would easily attain every other virtue, whereas without it not a single virtue can be firmly established.