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” (Shedd, 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, and God's dealings with Pharaoh in the book of Exodus).
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. For example, taking Romans 9:18-22 and the relevant Exodus account it is clear that God actively "necessitated" the action of Pharaoh to not let His people go in order to display His power in him.
“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” (Shedd, p. 317).
God’s decree IS contradictory to Shedd's presumed “free agency” and
this decree is MUCH MORE POWERFUL than his weakly defined “compulsion.”
Since God will NOT give or share His sovereign glory to creature man, Shedd irrationally
concludes that this would “disprove the Divine omnipotence.” Of course man's actions are voluntary. Pharaoh hardened his heart voluntarily. But that does not change the fact that God actively caused Pharaoh to harden his heart voluntarily and make him disobey in order to demonstrate holy wrath and power.
“‘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).
No, Shedd. God did not decree that man should share in some self-determining sovereignty. Only God is self-determining. And in the instance of sin, God DOES work in man "to will and to do" (cf. Philippians 2:13). Philippians 2:13 speaks to God's active working in the hearts of His people to do His good pleasure. This working of God in the hearts of the regenerate is different than God's work of hardening the reprobate in His providence, but His work is active in both cases. He actively worked in certain people and turned their heart to hate His people:
He TURNED their heart to hate His people, to deal craftily with His servants” (Psalm 105:25).
Psalm 105:25 is quite clear, as is the Biblical teaching of God's sovereign control over ALL the actions of men despite Shedd's impious attempt to muddy it up. This is NOT “inexplicable” at all for those who don’t attempt to hide their sedition under a cloak of “mystery.”