Rather than a regular book review I thought I might change things up a bit and give an outline of an essay by St. Justin Popovich, titled The Theory of Knowledge of St. Isaac the Syrian. This essay can be found in two books: Orthodox Faith and Life in Christ (pp. 117-168) and Man and God-man (pp. 67-106) (When I give page numbers in this post, they will be for the second book).
St. Justin begins by saying that our organs of understanding are sick and need healed (pp. 70-71). The passions are the sickness of the soul, so it is the virtues which are the cure. St. Justin also says that there is a chronological order to the virtues: First comes faith (pp. 72-75), which helps us concentrate on spiritual things and brings us peace; Second comes prayer (pp. 75-76), which is the language of faith, and is the struggle to redirect our focus more and more on God and less and less on oursleves; Third comes love (pp. 76-78), which is "born of prayer," and causes us to turn from love of self to love of God, and learn the true meaning of love; and Fourth comes humility (pp. 78-79), which is how one thinks by faith when focused on God rather than self.
All of this, St. Justin says, is done in Grace and freedom (pp. 79-81), and thus a person's intellect is purified, with help also coming from fasting, vigils, silence, etc. (pp. 81-85). Eventually we come to the mystery of knowledge (pp. 85-95), which is difficult to define. However, St. Justin believes that the "most exhaustive" answer that St. Isaac gives is that knowledge is the "perception of eternal life," and that the perception of eternal life is "to perceive all things in God." And so elsewhere St. Isaac defines truth as "The perception of things that is given by God." Or, as St. Justin rephrases it: "The perception of God is truth".
The final step is contemplation of God (pp. 95-103). Contemplation comes through the continual pondering on God. “It is the abode of unceasing prayer,” and “purity sees God.” St. Justin says that this contemplation of the Holy Trinity is the goal of the Christian life. They essay concludes (pp. 103-106) with St. Justin saying that “the problem of knowledge is fundamentally a religious and ethnical problem,” and that “One thing is certain: that knowledge on all levels, depends on man’s religious and moral state.”