***”If God,” say they, “wishes all men indiscriminately to be saved, it is false that some are predestined by his eternal purpose to salvation, and others to perdition...” ***
Now that is quick footwork. Scripture says ‘all men’ and not ‘all princes and kings’. Jesus will draw all men to Him when He ascends.
But you say, not all men will be saved. And you are correct. Therefore the problem is in the interpretation. A predestined future for all men is therefore incorrect because it only is supported by some of the verses in Scripture and strongly refuted by others.
***Does God regenerate all men?***
No. Nobody said He did.
***Is God’s saving grace to believe shed on all men? ***
Yes. His grace extends to all men.
***If that were true, there would be two saved thieves at Calvary instead of only one.***
Men are not robot slaves. Only one thief repented.
"In meekness instructing those that oppose themselves; if God peradventure will give them repentance to the acknowledging of the truth" -- 2 Timothy 2:25
If God gave all men saving grace, all men would be saved. Christ's atonement is sufficient for all the world, and efficient only for those whom God has graced with faith in Him.
Salvation by His grace through faith in Christ, as Paul tells us in Ephesians 2, is not of ourselves. It is a gift from God.