If you went through CCD as a child, as I did, you at least remember that there are two kinds of grace: sanctifying and actual. Keep in mind that they aren’t the same thing.
Sanctifying grace perdures in the soul. It’s what makes the soul holy; it gives the soul supernatural life. More properly, it is supernatural life. Actual grace, by contrast, is a supernatural impulsion. It’s transient. It doesn’t live in the soul but acts on the soul from the outside, so to speak. It’s a supernatural kick in the pants. It gets the will and intellect moving so we can seek out and retain sanctifying grace.
To illustrate, imagine yourself transported instantaneously to the bottom of the ocean. What’s the first thing you’ll do? That’s right: die. You’ll die because you aren’t equipped to live underwater. You don’t have the right breathing apparatus. If you want to live in the deep blue sea, you need equipment you aren’t provided with naturally—you need something that will elevate you above your nature, something super (above) natural, such as oxygen tanks.
It’s much the same with your soul. In its natural state, it isn’t fit for heaven. It doesn’t have the right equipment, and if you die with your soul in its natural state, heaven won’t be for you. What you need to live there is supernatural life, not just natural life. That supernatural life is called sanctifying grace. If it indwells your soul when you die, then you have the equipment you need, and you can live in heaven (though you may need to be cleansed first in purgatory). If it doesn’t indwell your soul when you die, too bad.
You can obtain supernatural life by yielding to actual graces you receive. God keeps giving you these divine pushes, and all you have to do is go along. For instance, he moves you to repentance, and if you take the hint you can find yourself in the confessional, where the guilt for your sins is washed away. Through the sacrament of penance, through your reconciliation to God, you receive sanctifying grace. But you can lose it again by sinning mortally.
Remember that word: mortal. It means death. Mortal sins are deadly sins because they kill off this supernatural life, this sanctifying grace. Mortal sins can’t coexist with the supernatural life, because by their nature such sins are saying “No” to God, while grace is saying “Yes.”
When you lose supernatural life, there’s nothing you can do on your own to regain it. You’re reduced to the merely natural life again, and no natural act can merit a supernatural reward. You can merit a supernatural reward only by being made able to act above your nature, which you can do only if you have help.
To regain supernatural life, you have to receive actual graces from God. Think of these as helping graces. Such graces differ from sanctifying grace in that they aren’t a quality of the soul and don’t abide in it. Rather, actual graces enable the soul to perform some supernatural act, such as an act of faith or repentance. If the soul responds to actual grace and makes the appropriate supernatural act, it receives again supernatural life.
Sanctifying grace implies a real transformation of the soul. Recall that the Protestant Reformers denied that a real transformation takes place. They said God doesn’t actually wipe away our sins. Our souls don’t become spotless and holy in themselves. Instead, they remain corrupted, sinful (full of sin) and God merely throws a cloak over them and treats them as if they were spotless, knowing all the while that they’re not.
But that isn’t the Catholic view. We believe souls really are cleansed by an infusion of the supernatural life. Paul writes of us as “in Christ a new creature” (2 Cor. 5:17), “the new man, who according to God is created in justice and holiness of truth.” Our souls don’t become something other than souls; they don’t cease to be themselves. Grace elevates nature. Our intellects are given the new power of faith, something they don’t have at the merely natural level. Our wills are given the new powers of hope and charity, things also absent at the merely natural level.
Moving on, I’ve mentioned that we need sanctifying grace in our souls if were to be equipped for heaven. Another way of saying this is that we need to be justified. “Now you have been washed clean and sanctified, and justified through the name of the Lord Jesus Christ and through the Spirit of our God” (1 Cor. 6:11). In Catholic theology, justification and sanctification go together. You’re justified so long as you’re sanctified. You cease to be justified when you cease to be sanctified. The heirs of the Reformers see justification differently. For them, justification is a legal declaration. If you “accept Christ as your personal Lord and Savior,” he declares you justified. You aren’t sanctified—your soul is the same as before—but you’re eligible for heaven. You’re expected thereafter to sanctify your life (don’t make the mistake of thinking Protestants say sanctification is unimportant), but the degree of sanctification you achieve is, ultimately, immaterial to the question of whether you’ll get to heaven. You will, since you’re justified.
Most Fundamentalists go on to say that losing ground in the sanctification battle won’t jeopardize your justification. You might sin worse than you did before “getting saved,” but you’ll enter heaven anyway, because you can’t undo your justification, which has nothing to do with whether you have supernatural life in your soul. Calvin taught the absolute impossibility of losing justification. Luther said it could be lost only through the sin of unbelief—that is, by undoing the act of faith—but not by what Catholics call mortal sins.
Catholics see it differently, of course. If you sin grievously, the supernatural life in your soul disappears, since it can’t co-exist with serious sin. You then cease to be justified. If you were to die while unjustified. you’d go to hell. But you can become rejustified by having the supernatural life renewed in your soul, and you can do that by responding to the actual graces God sends you. He sends you one, say, in the form of a nagging voice that whispers, “Repent! Go to confession!” You do, your sins are forgiven, you’re reconciled to God, and you have supernatural life again. Or you say to yourself, “Maybe tomorrow,” and that particular supernatural impulsion, that actual grace, passes you by. But another is always on the way, God never abandoning us to our own stupidity.
(Venial sins don’t destroy supernatural life, and they don’t even lessen it. Mortal sins destroy it outright. The trouble with venial sins is that they weaken us, making us more vulnerable to mortal sins.)
Once you have supernatural life, once sanctifying grace is in your soul, you can increase it by every good action you do: receiving Communion, saying prayers, performing the corporal works of mercy. Is it worth increasing sanctifying grace once you have it—isn’t the minimum enough? Yes and no. It’s enough to get you into heaven, but it may not be enough to sustain itself. It’s easy to fall from grace, as you know. The more solidly you’re wed to sanctifying grace, the more likely you can withstand temptations. And if you do that, you maintain sanctifying grace. In other words, once you achieve the supernatural life, you don’t want to take it easy. The minimum isn’t good enough because it’s easy to lose the minimum.