If I say... — Rather,
I say only let darkness crush me,
And light become night around me.
Commentators have mostly been frightened by the metaphor in the first line, though it has been preserved both by the LXX. and Vulg., and can only be avoided either by forcing the meaning of the verb from what it bears in Genesis 3:15; Job 9:17, or altering the text. Yet the Latins could speak even in prose of a region “oppressed by darkness” (Sen. Ep. 82); and when night was used as figurative of death, nocte premi was a common poetical figure. Indeed, the word rendered darkness here is actually, in Psalms 88:6, used of death, and if we understood this figure here we might render the word trample, illustrating by Horace
“Jam te premet nox fabulæque Manes.”
Such a view would suit the thought to which the poet immediately passes — to God the darkness of death and the nothingness before birth are alike. On the other hand, as the main thought is that nowhere is there escape from God’s sight in height, or depth, or distance so to exhaust the possibilities we seem to need, darkness.
The second clause does not begin the apodosis: it is in synthetic parallelism with the first.