A contemporary of Thomas Aquinas, Bonaventure was minister general (superior) of the Franciscans and one of the greatest of 13th century theologians and spiritual writers. Because of his skill in reconciling opposite views, he came to be regarded as his Order's second founder. The following is taken from his famous Mind's Ascent to God.
It seems amazing,
when it has been shown
that God is so close to our souls,
that so few should be aware
of the First Principle within themselves.
Yet the reason is close at hand:
for the human mind, distracted by cares,
does not enter into itself through memory;
clouded by sense images,
it does not turn back to itself through intelligence;
allured away but concupiscence,
it does not turn back to itself through desire
for inner sweetness and spiritual joy.
Thus lying totally in these things of sense,
it cannot re-enter into itself
as into the image of God….
No matter how enlightened you may be
by the light of natural and acquired knowledge,
you cannot enter into yourself
to delight within yourself in the Lord
unless Christ be your mediator, who says:
I am the door.
If anyone enters through me,
He will be saved;
and he will go in and out and will find pastures.