Brother Benjamin,
God's will is the first cause of all causes. This is scriptural and also logical. This is because God is the only thing that does not have a cause as He alone is eternal and created all things. "All things were made by him; and without him was not any thing made that was made." (John 1:3)
Ephesians 1:11 tells us, "him who worketh all things after the counsel of his own will:", therefore His will is the first cause of all causes.
Sin is carried out as a result of secondary causes. The secondary causes of sin are two different created creatures. # 1 is Satan, as it is written, "...the prince of the power of the air, the spirit that now worketh in the children of disobedience:" (Ephesians 2:2). The other secondary cause of sin is man's evil flesh, "For I know that in me (that is, in my flesh,) dwelleth no good thing" (Romans 7:18). Any good that is carried out by a regenerated child of God per scripture is a result solely of God working directly through his children by God's will, "For it is God which worketh in you both to will and to do of his good pleasure" (Philippians 2:13)
God willing that sin come into existence does not make God the author of sin. Please permit me to explain. An act alone does not constitute sin, but the righteousness or unrighteousness of an act is determined by the motive prompting the act. If a physician causes his fellowman great pain and suffering and even death by the amputation of a limb in an effort to do him good, no one would condemn that physician of wrong doing; but if he causes him pain or suffering or death by amputating a limb in malice and with an intention of doing him harm, that physician is guilty of wrong. God has a holy and sinless motive in all that He does, in all that He causes to be done and in all that He allows to be done, and intends that each thing done shall redound to the praise of that holy and exalted purpose, and so it matters not how sinful and vile the act may be when performed by man with a corrupt motive, God’s motive and purpose in the act being most holy He is not and can not be chargeable with sin; and yet the very same act which He has appointed to issue in His praise and redound to His glory is a vile transgression on the part of the one who performed it, as his design was evil.
To illustrate, when God sent the king of Assyria against Israel with the charge God declares “I dispatch him against a people who anger me, to seize loot and snatch plunder, and to trample them down like mud in the streets.” (Isaiah 10:6), God continues, “But this is not what he (the king of Assyria) intends,
this is not what he has in mind; his purpose is to destroy, to put an end to many nations”. (Isaiah 10:7) The wickedness was not put in the heart of the king by God’s decree, but it was already there. But God then states, “Wherefore it shall come to pass, that when the Lord hath performed His whole work upon mount Zion and on Jerusalem, I will punish the fruit of the stout heart of the king of Assyria, and the glory of his high looks. For he saith, by the strength of my hand I have done it, and by my wisdom...” (Isaiah 10:12-13) Read the entire 10th chapter of Isaiah. This wicked king did the very thing God determined, but he was not moved in the least to do it by God’s decree; he was entirely ignorant of that, but was actuated by an evil motive to cut off and destroy, thus God punished him for this! Thus we see that an act does not determine if something is sin, but the motive prompting the act, thus God can will that sin exist, but not be the author of sin.
God directly predetermined to do all acts of good on this earth and he predetermined that others would do all the acts of evil on this earth, but he has uses these evil acts to produce a greater good- Take for example, the crucifixion of Christ, the most evil act of mankind ever-was of God's predetermined plan according to scripture. "And truly the Son of man goeth, as it was determined: but woe unto that man by whom he is betrayed!" (Luke 22:22) Also, "26 The kings of the earth stood up, and the rulers were gathered together against the Lord, and against his Christ. 27 For of a truth against thy holy child Jesus, whom thou hast anointed, both Herod, and Pontius Pilate, with the Gentiles, and the people of Israel, were gathered together,28 For to do whatsoever thy hand and thy counsel determined before to be done. (Acts 4:26-28) and finally, "Him, being delivered by the determinate counsel and foreknowledge of God, ye have taken, and by wicked hands have crucified and slain" (Acts 2:23). He used these acts to bruise his Son, make him Sin, thus redeeming his people so they can live with and in him for all of eternity. This is the greatest act of love this world has or ever will see. Yet we also see those who did these acts are declared to be done by "wicked hands", therefore they are not excused by God in their actions even though it was used to fulfill God's purpose (these wicked men acted from their evil motives and were ignorant of God's Holy purposes He had in the whole matter).
Thus, through the crucifixion we see how God can predestinate the most evil act history has ever see, but at the same time have it about to His glory by accomplishing mercy, redemption, forgiveness, grace, justification, etc. Therefore, if He can do this with the most wicked act man has ever known, He can, and certainly does so for all lessor acts of evil, yet cannot be charged with being the "author of sin" as His motives behind his predestination/predetermination of events are always holy and just. I hope this long rambling reply has answered your questions and that you will now answer my question of, "Is God's will the first cause of all causes, if not, what is?"
God bless,
Brother Joe