The following quotes are from W.G.T. Shedd’s Dogmatic Theology, single volume edition:
“The Westminster Confession 3.1 affirms, that ‘the liberty or contingency of second causes is not taken away, but rather established’ by the Divine decree. If God has decreed men’s actions to be free actions, and as free actions, then it is impossible that they should be necessitated actions. His decree makes the thing certain in this case, as well as in every other. The question how God does this, cannot be answered by man, because the mode of the Divine agency is a mystery to him” (p. 317).
Shedd assumes without Biblical warrant that men are free relative to God’s decree. Since God has decreed men’s actions these actions are obviously NOT free. These actions ARE NOT “necessitated” by less-than-omnipotence, BUT they ARE “necessitated” by God’s omnipotent active causation and control (see Isaiah 10:5-16 & Romans 9:18-22). The “mode of the Divine agency” IS NOT a “mystery” as Shedd says. It’s just that Shedd does not like what the Bible teaches about it.
“The notion of a decree is not contradictory to that of free agency, unless decree is defined as compulsion, and it be assumed that God executes all his decrees by physical means and methods. No one can demonstrate that it is beyond the power of God to make a voluntary act of man an absolutely certain event. If he could, he would disprove the Divine omnipotence” (p. 317).
God’s decree IS contradictory to man’s (presumed) “free agency” and this decree is MUCH MORE POWERFUL than a weakly defined “compulsion.” Since God will NOT give His sovereign glory to man Shedd irrationally concludes that this would “disprove the Divine omnipotence.”
“‘God, the first cause, ordereth all things to come to pass according to the nature of second causes, either necessarily, or freely and contingently’ (Westminster Confession 5.2; 6.6.6). The self-determination of the human will is the action of a free second cause. It is therefore decreed self-determination. In the instance of holiness, the certainty of the self-determination is explicable by the fact that God works in man ‘to will and to do.’ In the instance of sin, the certainty of the self-determination is inexplicable, because we cannot say in this case that God works in man ‘to will and to do'” (Shedd, Dogmatic Theology, p. 317).
Of course it’s NOT “self-determination” on man’s part. And certainty in the instance of sin is NOT inexplicable as the following verse clearly shows:
“He TURNED their heart to hate His people, to deal craftily with His servants” (Psalm 105:25).
This is NOT “inexplicable” at all for those who don’t attempt to hide their sedition under a cloak of “mystery.”