Soon after Augustine became a Christian in the year 387, he had a mystical religious experience. It happened inside a villa in Ostia, which town was the port of Rome, located near the mouth of the Tiber River. Most of what is known of the event comes from the words of Augustine in his Confessions.
Augustine and his mother Monica "were alone and talking together and very sweet our talk was."
Looking out from a window at their garden, they began to discuss "what the eternal life of the saints could be like." Following upwards, step by step all the bodily items in the sky, they felt the touch of God "just lightly," and were at once overwhelmed with a mystical ecstatic experience. Augustine later wrote that "the greatest possible delights of our bodily sense, radiant as they might be with the brightest of corporeal light, could not be compared with the joys of that [spiritual] life."
In his Confessions, Augustine wrote that he had struggled both before and after Ostia to tap into this mystical higher reality. Inspired by his readings of philosophy, he concentrated on the ascent of his soul to this highest realm of the universe. His first attempts were during the year 386 in Milan. There his effort at envisioning the divine had been fleeting and disappointing.
He believed that his lack of moral strength at that time had prevented him from sustaining any lasting union with the divine. Yet he had realised that achieving a mental, spiritual union with God was the ultimate happiness one could hope to ever achieve in life. In his Confessions, Augustine not only reported on the successes of his mystical experiences, but explained the methods by which one could advance "step by step" to ever higher realms of the divine. A person must mentally focus his mind inwardly towards his soul, and leave all thought of the material world behind. Then, "in a flash of a trembling glance", one could possibly achieve union with God. Augustine described such moments as "a kind of sweet delight." But to remain in such a state forever would not be something of this world. It would be "not of this life, but of the life to come."
To Augustine, these feelings were an experience of what existence with God in heaven would be like. To experience this, Augustine had given up his previous life and replaced it with the life of an active Christian person. Rather than his previous strange prayer, "Lord, make me chaste, but not yet!" he now prayed, "May your Scriptures be my chaste delight. As to whether to classify Augustine as a mystic, scholars are reluctant, because only traces of his mysticism are evident.
Link
Ostia. The Harbour City of Ancient Rome http://www.ostia-antica.org AN1112