O LORD, you have searched me and known me!
You know when I sit down and when I rise up;
you discern my thoughts from afar.
You search out my path and my lying down,
and are acquainted with all my ways,
Even before a word is on my tongue,
behold, O LORD, you know it altogether.
For you formed my inward parts,
you knitted me together in my mother's womb.
I praise you, for you are awesome and wonderful.
Wonderful are your works!
Your eyes beheld my unformed substance;
in your book were written, every one of them,
the days that were formed for me,
when as yet there was none of them.
How precious to me are your thoughts, O God!
How vast is the sum of them!
If I could count them, they are more than the sand.
Ps 139, 1-4, 13-18. RSV-SCE
Those who sensed keenly, and almost all saints are an instance of this, the futility of escaping God's pursuit of the soul, must have found in this psalm a mirror for their experience. A memorable expression of this is Francis Thomson's poem, "The Hound of Heaven."
This psalm contains for modern man more valuable material for reflection than a psychological, introspective plumbing of one's motivations. The material, once properly grasped, exposes one to that mental sanity which is sound philosophy of which there is aplenty in this psalm. This is indeed the most philosophical of all psalms. Its main theme is God's omnipresence and omniscience. Most of the times the point is put across in distinctly poetic terms, such as the fastness of the wings of the dawn and the brightness of even the darkest night. But at other times the diction is worthy of the finest metaphysical poets. Only those would be taken aback by this who let themselves be blinded by the cliché that there is a radical difference between Greek metaphysical rationality and biblical existentialism. Once one admits that good philosophy begins with wonderment and keeps exuding it, it will be easy to see metaphysics blare forth from this psalm, which in fact contains utterances about infinity that no mathematician can improve upon.
And if one sees that the difference between wonderment and assent is not an opposition but a complement, one's conversion to metaphysics, as recommended by this very "biblical" psalm, may be complete. It is a metaphysics vibrant with vitality, including its spiritual kind. True enough, the Bible stands or assent, but never for a blind one. Faith, as Paul insisted (Rom 12:1), ought to be a logike latreia, a truly reasonable and well-reasoned service, a point that cannot be recalled often enough.
Those desirous of a truly perennial philosophy may find it articulated in a capsule form in this psalm. By praying this psalm devoutly we may go a long way toward obtaining the grace which is the true love of wisdom. The word "philosophy" means precisely this insofar as it aims at truth and not merely at opinions about it.
[S.L. Jaki, Praying the Psalms pp. 226-7]