fellow who espouses hyper-Calvinism wrote me to argue that there is no such thing as "common grace." He insisted that God's "apparent goodness" to the reprobate has no other purpose than to increase their condemnation. He was convinced that God is as active in making the reprobate wicked as He is in conforming the elect to the image of Christ. And for "proof," he cited Romans 5:20: "The law entered that the offense might abound."
My view, of course, is different from his.
So let's think through some of these issues carefully. Consider, first of all, that the law has the effect of provoking sin in the elect as well as the reprobate. Even the apostle Paul testified that the tenth commandment stirred up all manner of coveting in his heart (Romans 7:8). He went on to explain in verse 13 that this is because the law was given to make sin appear exceedingly sinful. In other words, the law makes sin abound in order to confront us with the reality and magnitude of our sin.
But that is ultimately a gracious purpose, and the second half of Romans 5:20 makes that point inescapable: "The law entered that the offense might abound. But where sin abounded, grace abounded much more." So the exacerbating of sin is not an end in itself. God's ultimate purpose, and that which He delights in, is not the sin, but the superabounding grace.
Moreover, even while the law is provoking us to rebellion, the Lord through common grace usually restrains sinnersincluding the reprobatefrom giving full expression to their sin (cf. Genesis 20:6; Romans 2:14-15).
So it is my conviction that the overall effect of common grace on the reprobate will be to decrease their condemnation, not increase it.
But what about the potter-clay analogy in Romans 9? my hyper-calvinist correspondent wondered.
We need to think that through carefully, too. The potter starts with a lump of claysomething inherently filthy and base, with hardening properties already defining its very nature. So the clay is analogous to fallen humanityuseless for anything at all except in the hands of the heavenly Potter.
Left alone, clay will harden into something permanently worthless. But when a skilled potter applies His work to that amorphous lump of filthy clay, he always makes it useful. He improves the clay-lump into something that can be employed for good purposes.
The end-products are of varying quality, of course, because they are made for different purposes. Sometimes the potter makes fine pottery that may include veritable works of art; other times he makes ash trays. But he starts with the same glob of clay, and all his finished products are superior to the worthless lumps they would have been apart from His work.
That's exactly what Paul meant when he spoke of vessels of honor and dishonor. "Dishonorable" vessels in Paul's analogy would be things like diaper pails, chamber pots, spittoons, garbage containers, and whatnot. The vessel used in such a way is "dishonorable" in the sense that you don't put it on display for honored guests, or use it to serve your Thanksgiving Turducken. (Or pizza, as the case may be.) But the potter who makes such dishonorable vessels isn't himself dishonorable. Nor are his purposes dishonorable. On the contrary, they are good. (Imagine a world without garbage containers.)
So the potter imagery does not suggest that God works to make the reprobate worse or worse off than they would have been without His work, nor does it suggest that He delights in increasing their condemnation. In fact, if their damnation is ultimately exacerbated in any sense because of His work, it is precisely because they have despised and spurned His goodness, which ought to lead them to repentance (Romans 2:4)not because He deliberately made them into something worse than they would have been otherwise. If they are worse off because of His goodness to them, it is their own fault. His goodness is not a mask for some hideous secret delight over their damnation.
The example of Pharaoh, cited by Paul in Romans 9, is a case in point. We are not to imagine that the potter-clay imagery suggests God made Pharaoh evil. The proclivity of Pharaoh's heart was already evil. Pharaoh's hatred for God and the things of God was Pharaoh's own character flaw, certainly not something God was responsible for.
Let me give you an illustration. When I was in high school, I had an old car, a beautiful 1954 Chevrolet Bel Aire. (I wish I still had it.) But in those days it was not quite the antique it would be today, and far from being a classic, it had some rather severe mechanical problems. One was that it steered left all the time. If I wanted to make it go straight down the road, I had to exert a steady pull to the right. But if I wanted to change to the left lane, I simply had to release that pressure, and the car would automatically veer left.
God exercises His sovereignty over an evil heart very much like that. The heart of Pharaoh was in God's hands so that He could turn it whithersoever He willed (Proverbs 21:1). But when it served God's sovereign plan for Pharaoh to turn stubborn, God did not have to exert force to pull him in an evil direction. God did not need to infuse an evil intention into Pharaoh's heart. God simply withdrew His influence and Pharaoh's own evil inclination steered him into the left lane, fulfilling God's plan.
John Calvin has an interesting section dealing with this very issue in his Institutes. (II.4.3) He writes:
God is very often said to blind and harden the reprobate . . .. There are two methods in which God may so act.  When his light is taken away, nothing remains but blindness and darkness: when his Spirit is taken away, our hearts become hard as stones: when his guidance is withdrawn, we immediately turn from the right path: and hence he is properly said to incline, harden, and blind those whom he deprives of the faculty of seeing, obeying, and rightly executing.So when Scripture says that God hardened Pharaoh's heart, we are not to think God infused an evil desire into Pharaoh, or sovereignly steered him in a direction Pharaoh was himself not inclined to go. Pharaoh's own will was already inclined toward evil; God simply permitted Pharaoh to fulfill the already-evil intentions of his own fallen heart and will. Or in other words, God sealed the will of Pharaoh in its own evil intention, and then used Pharaoh's evil designs to accomplish God's good purposes.
 The second method . . . is when executing his judgements by Satan as the minister of his anger, God both directs men's counsels, and excites their wills, and regulates their efforts as he pleases.
In fact, God's agency in hardening Pharaoh's heart is exactly like the agency of the sun in hardening clay. The sun is in no way tainted or influenced by its contact with the clay; but the clay is profoundly affected by the sun's rays.
Furthermore, the property that gives clay its hardness is a property that belongs to the clay, not the sun. Want proof? Put a block of ice in the sun and see what happens to that. It will melt rather than harden. So the property that leads to the hardening of clay is something in the clay. Left to itself the clay will harden with or without exposure to the sun's bright light. The sun merely accelerates the natural process.
And that is precisely the effect the Word of God had on Pharaoh. So while we may truly say that God hardened Pharaoh's heart, it is vital to remember that the sinful properties that caused the hardening lay in Pharaoh's own heart. Pharaoh alone was responsible for his stubbornness. God, though sovereignly in control from beginning to end, bore no responsibility whatsoever for the evil that emanated from Pharaoh's own will.