Antinomianism, or as it has been labeled by some today Free Grace Theology, is the idea that you can accept Christ as Savior, leaving the issue of his Lordship optional, and yet still be reckoned "saved". That is the idea that one can for example pray to receive Jesus into their hearts and then continue to willfully live a lifestyle of sin and yet presume that such a person will escape the wrath of God. Some even go so far with this as to propose that one could fall away into unbelief and yet still be reckoned saved so long as at some time in the past you had "believed" or prayed the sinner's prayer or such. Much as this idea may be popular in modern evangelicalism, it is neither consistent with the Bible, nor with Calvin's Theology.

Perseverance of the Saints, as it is referred to as the 5th point of Calvinism. The Westminister Confession speaks of the Perseverance of the Saints saying:

I. They, whom God hath accepted in His Beloved, effectually called, and sanctified by His Spirit, can neither totally, nor finally, fall away from the state of grace: but shall certainly persevere therein to the end, and be eternally saved.

II. This perseverance of the saints depends not upon their own free will, but upon the immutability of the decree of election, flowing from the free and unchangeable love of God the Father; upon the efficacy of the merit and intercession of Jesus Christ; the abiding of the Spirit, and of the seed of God within them; and the nature of the covenant of grace; from all which ariseth also the certainty and infallibility thereof.

III. Nevertheless, they may, through the temptations of Satan and of the world, the prevalency of corruption remaining in them, and the neglect of the means of their preservation, fall into grievous sins; and, for a time, continue therein: whereby they incur God's displeasure, and grieve His Holy Spirit, come to be deprived of some measure of their graces and comforts, have their hearts hardened, and their consciences wounded, hurt and scandalize others, and bring temporal judgments upon themselves.

Now if you read this third point you can infer some antinomian theology. And so you can also infer the same idea from Calvin's commentary of 1John 3:9 concerning his comments on David's fall. However many today misunderstand Reformed Theology of teaching that it is God who perseveres and that in fact it should not be the Perseverance of the Saints but the Preservation of the Saints in a once saved only saved sense, without there being necessarily any correlation to their behavior or perseverance in their behavior. It is this point which is not really clarified in the Westminister Confession, which is quite vague on the issue. But Calvin's commentary on 1John 3:9 from which this point in the Confession was derived, and in which he even uses the word "perseverance", states clearly:

"the hearts of the godly are so effectually governed by the Spirit of God, that through an inflexible disposition they follow his guidance." (John Calvin)

"the power of the Spirit is so effectual, that it necessarily retains us in continual obedience to righteousness." (John Calvin)

This is not eternal security. Rather Perseverance of the Saints is a perseverance in a behavior consistent with that expected of a child of God.

But is Calvin speaking of "Perfect Sanctification" in a Charles Finney sense as many "holiness" types speak of it today, in which a person never commits any particular sin, or is only righteous as long as they don't sin? No. For he says, "But John does not speak of one act, as they say, but of the continued course of life." (John Calvin)John the Apostle is speaking of the person's overall life as a Christian. Those those born of God may fall from time to time, you won't find one who lives a lifestyle of sin. Or to say it another way, if you find a Christian who lives a lifestyle of sin, then you've found a "Christian" who is not born of God.

John 7:39  But this He spoke concerning the Spirit, whom those believing in Him would receive; for the Holy Spirit was not yet given, because Jesus was not yet glorified.

"And he cannot sin." Here the Apostle ascends higher, for he plainly declares that the hearts of the godly are so effectually governed by the Spirit of God, that through an inflexible disposition they follow his guidance. This is indeed far removed from the doctrine of the Papists. The Sorbons, it is true, confess that the will of man, unless assisted by God's Spirit, cannot desire what is right; but they imagine such a motion of the Spirit as leaves to us the free choice of good and evil. Hence they draw forth merits, because we willingly obey the influence of the Spirit, which it is in our power to resist. In short, they desire the grace of the Spirit to be only this, that we are thereby enabled to choose right if we will. John speaks here far otherwise; for he not only shews that we cannot sin, but also that the power of the Spirit is so effectual, that it necessarily retains us in continual obedience to righteousness. Nor is this the only passage of Scripture which teaches us that the will is so formed that it cannot be otherwise than right. For God testifies that he gives a new heart to his children, and promises to do this, that they may walk in his commandments. Besides, John not only shews how efficaciously God works once in man, but plainly declares that the Spirit continues his grace in us to the last, so that inflexible perseverance is added to newness of life. Let us not, then, imagine with the Sophists that it is some neutral movement, which leaves men free either to follow or to reject; but let us know that our own hearts are so ruled by God's Spirit, that they constantly cleave to righteousness.

Moreover; what the Sophists absurdly object, may be easily refuted: they say that thus the will is taken away from man; but they say so falsely: for the will is a natural power; but, as nature is corrupted, it has only depraved inclinations. It is hence necessary that the Spirit of God should renew it, in order that it may begin to be good. And, then, as men would immediately fall away from what is good, it is necessary that the same Spirit should carry on what he has begun, to the end.

As to merit, the answer is obvious, for it cannot be deemed strange that men merit nothing; and yet good works, which flow from the grace of the Spirit, do not cease to be so deemed, because they are voluntary. They have also a reward, for they are by grace ascribed to men as though they were their own.

But here a question arises, Whether the fear and love of God can be extinguished in any one who has been regenerated by the Spirit of God? for that. this cannot be, seems to be the import of the Apostle's words. They who think otherwise refer to the example of David, who for a time labored under such a beastly stupor, that not a spark of grace appeared in him. Moreover, in the fifty-first Psalm, he prays for the restoration of the Spirit. It hence follows that he was deprived of him. I, however, doubt not but that the seed, communicated when God regenerates his elect, as it is incorruptible, retains its virtue perpetually. I, indeed, grant that it may sometimes be stifled, as in the case of David; but still, when all religion seemed to be extinct in him, a live coal was hid under the ashes. Satan, indeed, labors to root out whatever is from God in the elect; but when the utmost is permitted to him, there ever remains a hidden root, which afterwards springs up. But John does not speak of one act, as they say, but of the continued course of life.

Some fanatics dream of something I know not what, that is, of an eternal seed in the elect, which they always bring from their mother's womb; but for this purpose they very outrageously pervert the words of John; for he does not speak of eternal election, but begins with regeneration.

There are also those who are doubly frantic, who hold, under this pretense, that, everything is lawful to the faithful, that is, because John says that they cannot sin. They then maintain that we may follow indiscriminately whatever our inclinations may lead us to. Thus they take the liberty to commit adultery, to steal, and to murder, because there can be no sin where God's Spirit reigns. But far otherwise is the meaning of the Apostle; for he denies that the faithful sin for this reason, because God has engraven his law on their hearts, according to what the Prophet says (Jeremiah 31:33.)