I'm not too far into the first volume, but something that has immediately jumped out at me is how the Orthodox monastic writers in the Philokalia deploy a psychological reading of Scripture. You may have heard about how many of the church fathers used an allegorical method of reading the Bible, especially the Old Testament. In this way of reading, events in the Old Testament aren't read literally, but are, rather, read as allegories about the spiritual life or as prefigurements of Christ. Few modern readers of Scripture would dare to read the Bible in this way, but it was quite common among the church fathers.
But when I say that the Philokalia employs a psychological reading of the Bible, I don't mean allegorical. I do mean psychological. Specifically, in the Philokalia many Biblical texts are read as applying to our mental life. A frequent example is reading references to the "enemy" in the book of Psalms as referring to mental temptations (typically associated with demonic attacks). Our "enemies" are seductive or disturbing thoughts. Relatedly, the violence of the imprecatory Psalms is understood to be directed at mental temptations and the demons who are causing them.
Here's an example from Evagrios the Solitary. He writes:
To quote the Psalm again, 'I have seen violence and strife in the city' (Ps. 55:9). So seek out places that are free from distraction, and solitary.
The "city" here is your mind. And in our minds there is "violence" and "strife." Thus, the recommendation is to seek out solitary places free from distraction.
Here's another example from Isaiah the Solitary:
If you cleave to God you will not be shaken by the passions; for it is written: 'They that trust the Lord shall be as Mount Zion; he that dwells in Jerusalem shall never be shaken' (Ps. 125:1).
Dwelling on "Mount Zion" and in "Jerusalem" is taken to mean not being shaken by the passions. The mind is a secure mountain, steady and free from mental perturbations.
This psychological approach to reading Scripture, understanding the physical and historical images of the Bible as referring to the mind and mental events, may also be common in the Western monastic tradition. But reading the Philokalia has introduced this approach to me.