Richard has posed a quote from Cole on the theme of the psalter. Much as I have benefited from Cole's paper on psalms 1, 2 and 149, I think that a single word can sum up the theme of the psalter: praise.
Why do I pick this one word? Because of the cumulative weighting of praise (הַלְל) in Book 5 as the chart on the left shows. One could also read into the weighting of forever in book 5, לְעוֹלָם - so there it is - praise for ever. I expect that תהלים, the name for the Psalms that is traditional in Hebrew thought, comes from similar observation. Psalm 22:3 captures it also: יוֹשֵׁב תְּהִלּוֹת יִשְׂרָאֵל - enthroned on the praises of Israel. John Hobbins has a nice expansion on the word praise here.
Eventually, I want to move from the multi-thematic frequently used words of the Psalter to this single aspect of praise. How does such a theme arise out of a long and tortuous tradition and an equally long and fractious history? How does it unify the movement from the wicked to the saints exemplified by the plural of Psalm 1 and the judgment of the plural חֲסִידִים in Psalm 149? This word is usually rendered as saints - but it is like its root, chesed, untranslatable. It means those to whom God has shown his chesed or those who are under God's protection, in this case loving kindness or mercy as shown through the covenant. (Lots of words for one word!)
We have seen the words that suggest to us that there are many themes in the Psalter: Whether it is the 8 repeated words of Psalm 119 that expand on the nurturing love of God for each individual and for the chosen, or whether it is the promise of covenant and the lament at its difficulty that pervades books 1 to 3, it is clear that enemies, troubles, sins, and failures, mercy, delight, and joy of the people - both chosen and otherwise - provide the context in which faith and trust in God's instruction are expressed.
I want also to return to my first questions on this blog over two years ago: why it is that there is no trumping of tradition by the words of Jesus in the letter to the Hebrews? Rather the tradition itself speaks of the anointing of the people and of the embodied dialogue of God with his equally concrete chosen anointed from the beginning, in the record of their lives and in the life of the nation.