We will now examine 2 Pet. 2:20-22:
 “For if after they have escaped the defilements of the world by the knowledge of the Lord and Savior Jesus Christ, they are again entangled in them and are overcome, the last state has become worse for them than the first.  For it would be better for them not to have known the way of righteousness, than having known it, to turn away from the holy command delivered to them.  It has happened to them according to the true proverb, ‘A dog returns to its own vomit,” and, “A sow, after washing, returns to wallowing in the mire.’” [NASB]
Peter may be further describing the apostasy of the false teachers who are the subjects of verses 1-17. The language of these verses strongly suggests that these false teachers had been true believers before their full submission to their sinful nature and defection from the faith. The Lord had “bought them” (2:1, cf. 1 Cor. 6:20; 7:22, 23). They denied His Lordship by submitting to their sinful nature (vss. 1-22). They have “left the straight way” and “gone astray” (vs. 15). Jude describes these same false teachers who “turn the grace of God into licentiousness” as “twice dead” (vs. 12) suggesting that they had once experienced spiritual life.
Peter may also be describing the awful state of those who have been led astray by these false teachers. In verses 18 and 19 we find that these false teachers were deceiving those who had just barely escaped “the ones who live in error”. In either case, the important point is that Peter is describing apostates, and that Peter understands these apostates to have been truly saved before becoming “again entangled” in the corruption from which they had previously escaped. Peter makes it clear that this “escape” came by way of “the knowledge of the Lord and Savior Jesus Christ”. There is every reason to believe that when Peter refers to these apostates as ones who had come to this “knowledge” of “Christ” that he means that this knowledge resulted in salvation. To say otherwise would suggest that there are means other than the shed blood of Jesus Christ by which a sinner may escape the corruption in the world. Such a concept is alien to the entire NT and is certainly alien to the inspired Apostle.
It is further significant that the Greek word for “knowledge” used in this passage is epignosis. This Greek word is predominately used by NT writers with reference to a full and complete knowledge, in contrast to an investigative or superficial knowledge (gnosis). Strong says of epignosis, “full discernment” [Strong's Exhaustive Concordance, #1922]. Kittel says, “The compound epignosis can take on almost a technical sense for conversion to Christianity” [Theological Dictionary of the New Testament, 121]. Vine’s Expository Dictionary of Old and New Testament Words says of gnosis, “primarily a seeking to know, an enquiry, investigation”, and of epignosis- “denotes exact or full knowledge, discernment, recognition, and is a strengthened form of No. 1 [gnosis], expressing a fuller or a full knowledge, a greater participation by the knower of the object known, thus more powerfully influencing him” [pg. 631]. The NASB renders epignosis as “real knowledge” in Phil. 1:9, and “true knowledge” in 2 Pet. 1:3, 8. In Col. 1:9 epignosis has reference to “all spiritual wisdom and understanding” and “a spirit of wisdom and revelation” in Eph. 1:17 (also see Philemon 4-6). Especially consider the salvation language of 1 Tim. 2:3, 4, “This is good and acceptable in the sight of God our Savior, who desires all men to be saved and come to the knowledge [epignosis] of the truth”.
We would especially expect Peter to use the weaker form of the word in 2:20 given the fact that Peter uses the stronger sense in 1:3, of which there is no doubt that true believers are being described. That Peter used the same word with the same object (“knowledge of Him”, “knowledge of… Jesus Christ”) to describe these apostates suggests that he was not describing false converts in 2:20 (see below regarding parallel language). Epignosis and gnosis are sometimes used interchangeably in Scripture but the stronger sense of epignosis should not be ignored, especially since Peter seems to use epignosis with specific reference to saving knowledge throughout this epistle. Peter’s choice of epignosis in 2:20, therefore, gives us further reason to identify these apostates as having been truly saved prior to their defection.
Peter’s deliberate use of parallel language in 2:20-22 with that used in 1:1-4 is even more striking. In 1:1-4 Peter describes his readers as those having a “faith…the same kind as ours” who have received the gift of “life” and “godliness” through the “knowledge of Him who has called us by His own glory and excellence”. He tells them that it is by these gifts of life, godliness, and knowledge that they have “become partakers of the divine nature” and have “escaped the corruption that is in the world by lust”. The parallels with those described in 2:20-22 are remarkable:
“Through our knowledge of him…participate in the divine nature” and “escaped the corruption in the world…” (1:3, 4)
“…escaped the corruption in the world by knowing our Lord and Savior Jesus Christ…” (2:20)
There is every reason to think that Peter is describing believers in both 1:1-4 and in 2:20. It is extremely strained exegesis to insist that those who “participate in the divine nature” and “escaped the corruption in the world” are of a different sort then those who “escaped the corruption in the world by knowing our Lord and Savior Jesus Christ”.
Some will say that those described in 2:20-22 only “appeared” to have escaped from the corruption in the world. There is no contextual warrant for this assumption. If these apostates had only “appeared” to escape the corruption in the world, then what sense does it make to say that they have become “again entangled” in these corruptions?
John Goodwin wrote of those who would be so bold as to claim that these “apostates” were:
…all this while most damnable hypocrites and dissemblers. Now that the Holy Ghost should say, that unbelievers, persons inwardly full of wickedness and filthiness, most vile hypocrites and dissemblers, have ‘escaped the pollutions of the world,’ especially ‘through the knowledge’ (or rather acknowledgment), en epignosei ‘of the Lord and Savior Jesus Christ,’ is to me, and I think to all other impartially considering men, the first-born of incredibilities. Can a man be said to escape his enemies when he still remains under their power, and is in greater danger of suffering mischiefs from them than ever before? Or is not he, who being enlightened, retains the truth in unrighteousness, remains inwardly full of malice and wickedness, only garbing himself with a hypocritical outside, or mere profession of holiness, as much or more under the power and command of sin, as likely to perish everlastingly for sin, as ever he was, or could be before his illumination? (Redemption Redeemed, ed., John Wagner, pg. 115)
Some look to avoid the implications of this passage by laying great stress on the nature of the animals described in the proverb given in verse 22, “It has happened to them according to the true proverb, ‘A dog returns to its own vomit,” and, “A sow, after washing, returns to wallowing in the mire.’” They say that the ones described in verses 20-21 must be only hypocrites and false converts because Peter would never describe them as “dogs” and “pigs” had they at one time been Christ’s “sheep”. Since Peter describes them as dogs and pigs, we should rest assured that their natures had never been changed by true conversion and regeneration.
Robert Shank rightly notes that:
Many have contended that the men of whom Peter wrote never were truly saved. They appeal to the metaphors in verse 22. God’s children, say they, cannot be referred to as dogs or sows. But they who assume that Peter’s reference to apostates as ‘dogs’ or ‘sows’ proves that they never were actually under grace do not likewise assume that Jeremiah’s reference to the children of Israel in Judah as “a wild ass” proves that they never were ‘the sheep of his pasture.’ The shameful epithet was applied by Jeremiah (2:4) only after the people had forsaken the Lord (2:13; 17:13) and turned aside in iniquity and idolatry. Likewise, it is only after they ‘have forsaken the right way and are gone astray’ that Peter likens apostates to dogs and sows. He could well have referred to them as “wild asses.’ But there were familiar proverbs about dogs and sows which so aptly illustrated their case. Let us accept the record at face value. To ignore the obvious meaning of Peter’s statements by resorting to arbitrary assumptions concerning his use of metaphors is, to say the least, unwise. (Life In The Son, pp. 175, 176)
The early Methodist theologian John Fletcher made the following observations concerning the contention that the Lord’s “sheep” can never cease to be anything other than “sheep”:
Multitudes, who live in open sin, build their hopes of heaven upon a similar mistake; I mean, upon the unscriptural idea which they fix to the Scriptural word sheep. “Once I heard the Shepherd’s voice,” says one of these Laodicean souls; “I followed him, and therefore I was one of his sheep; and now, though I follow the voice of a stranger, who leads me into all manner of sins, into adultery and murder, I am undoubtedly a sheep still: for it was never heard that a sheep became a goat.” Such persons do not observe, that our Lord calls “sheep” those who hear his voice, and “goats” those who follow that of the tempter. Nor do they consider that if Saul, a grievous wolf, “breathing slaughter” against Christ’s sheep, and “making havoc” of his little flock, could in a short time be changed both into a sheep and a shepherd; David, a harmless sheep, could, in as short a time, commence a goat with Bathsheba, and prove a wolf in sheep’s clothing to her husband.
He then offers the following “ridiculous soliloquy” to “…show the absurdity and danger of resting weighty doctrines upon so sandy a foundation as the particular sense which some good men give to a few Scriptural expressions”:
Those very Jews whom the Baptist and our Lord called ‘a brood of vipers and serpents,’ were soon after compared to ‘chickens,’ which Christ wanted ‘to gather as a hen does her brood.’ What a wonderful change was here! The vipers became chickens! Now, as it was never heard that chickens became vipers, I conclude that those Jews, even when they came about our Lord like ‘fat bulls of Bashan,’ like ‘ramping and roaring lions,’ were true chickens still. And indeed, why should not they have been as true chickens as David was a true sheep when he murdered Uriah? I abhor the doctrine which maintains that a man may be a chick or a sheep today, and a viper or a goat to-morrow.
But I am a little embarrassed. If none go to hell but goats, and none to heaven but sheep, where shall the chickens go? Where ‘the wolves in Sheep’s clothing?’ And in what limbus of heaven or hell shall we put that ‘fox Herod,’ the dogs who ‘return to their vomit,’ and the swine, before whom we must ‘not cast our pearls?’ Are they all species of goats, or some particular kind of sheep? “My difficulties increase! The Church is called a dove, and Ephraim a silly dove. Shall the silly dove be admitted among the sheep? Her case seems rather doubtful. The hair of the spouse in the Canticles is likewise said to be like ‘a flock of goats,’ and Christ’s shepherd are represented as ‘feeding kids, or young goats, beside their tents.’ I wonder if those young goats became young sheep, or if they were all doomed to continue reprobates! But what puzzles me most is, that the Babylonians are in the same verse compared to ‘lambs, rams, and goats.’ Were they mongrel elect, or mongrel reprobates, or some of Elisha Coles’ spiritual monsters? (Works of Fletcher Vol. 1, pp. 197-199, Wesleyan Heritage Collection CD)
Robert Picirilli concludes his treatment of 2 Pet. 2:22 with the following observation:
Those who attempt to mitigate Peter’s teaching by suggesting that the real nature of the sow or the dog had not been changed, and that this implies that these apostate false teachers were never regenerated, are pressing the illustrations beyond what they are intended to convey. Indeed, the proverb must be interpreted by the clearer words that precede them and not the other way around. The previous paragraphs express precisely what the proverbs were intended to convey (Grace, Faith, Free Will, pg. 232)
Picirilli is quite right that we need to look to the clear language of the passages that precede this descriptive proverb in order to properly understand Peter’s intended meaning. It is desperate exegesis to make assumptions based on the nature of the animals described in the proverb and then try to read them back into the plain teaching of verses 20 and 21. The claim that these “dogs” and “pigs” could only refer to those who had never truly been sheep ignores the context of the entire chapter. It foolishly trivializes the fact that Peter describes these apostates as having truly “escaped” the corruption in the world through “the knowledge [epignosis] of our Lord and Savior Jesus Christ” before becoming “again entangled” in this corruption. It further ignores the exegetical relevance of the parallel description in 2 Pet. 1:1-4 which uses nearly identical language to describe those of “like faith” who are “partakers of the divine nature”. The use of the proverb was to further illustrate the apostates’ return to corruption. That is quite the opposite of demonstrating that they had never escaped corruption. Just as a dog returns to that from which it had been purged, and a washed pig returns to the mire, so have these apostates, after having escaped from corruption, returned again to those defilements.
Still others might acknowledge that these apostates were once truly regenerated while insisting that they shall only lose heavenly rewards and not salvation. How then could Peter say of them that “it would be better for them not to have known the way of righteousness, than having known it, to turn away from the holy command delivered to them”? How could it possibly be better to have never known the way of righteousness, and perish forever, than to have known the way of righteousness only to lose some heavenly rewards? Do the advocates of this position truly believe that those who enter the joys of Heaven with considerably less rewards are worse off than those who will eternally suffer in Hell?
Despite the efforts of some to rescue their theology from the plain teaching of 2 Pet. 2:20-22, these passages serve as a stark reminder that those who have come to a saving knowledge of Jesus Christ may yet return to a lifestyle of sin ,abandon their faith, and perish in that hopeless state.