Knowledge

I feel that a point made in Augustine's On Christian Teachings that could be used to interpret the Psalms is found early on, when Augustine talks about the seven stages toward finding wisdom.  The third stage, knowledge, could be used to help us interpret The Book of Psalms.  Being the third stage right after fear and holiness, this stage is reachable by almost every person which makes is relatable because many of the people who read the psalms are average ordinary people looking for guidance.  

In this stage, "every student of divine scripture exerts himself ... and will find that he must love god with his whole heart, his whole soul, and his whole mind, and his neighbor as himself - in other words, his love for his neighbor should be totally related to God." In reference to the Psalms, one has to love god entirely because sometimes God will do things which one may not understand.  "It is at this point that the fear which makes him ponder the judgement of God, and the holiness which makes it impossible for him not to admit and submit to the authority of the holy books, compel him to deplore his own condition." In reference to this are the psalms of supplication, where it seems God has left and one must ask him to return and give help.  In order for God to return and offer aid, one must leave fear behind and continue to believe in God or he may be lost forever. 

Also, there are many psalms which include violence.  This could be read as the violence occurring when the love for neighbors is broken and is no longer related to God.  If one loves his neighbor just like his own self-love, then there would be no violence or bloodshed, but rather knowledge and love for one another.  The third stage of knowledge is applicable to all, and is also has connections to many of the Psalms, thus making the third stage of knowledge very useful when interpreting the Psalms.