It is best to see what Scripture has to say about it, before we seek to answer this question. We read, "For if after they have escaped the pollutions of the world through the knowledge of the Lord and Savior Jesus Christ, they are again entangled therein, and overcome, the latter end is worse with them than the beginning. For it had been better for them not to have known the way of righteousness, than, after they have known it, to turn from the holy commandment delivered unto them. But it is happened unto them according to the true proverb, The dog is turned to his own vomit again; and the sow that was washed to her wallowing in this mire." (2 Peter 2:20-2220For if after they have escaped the pollutions of the world through the knowledge of the Lord and Saviour Jesus Christ, they are again entangled therein, and overcome, the latter end is worse with them than the beginning. 21For it had been better for them not to have known the way of righteousness, than, after they have known it, to turn from the holy commandment delivered unto them. 22But it is happened unto them according to the true proverb, The dog is turned to his own vomit again; and the sow that was washed to her wallowing in the mire. (2 Peter 2:20‑22)).
One thing is certain, the Scriptures would never describe a true Christian, a child of God, as a dog. Dogs always stand in Scripture for evil persons. We read, "Beware of dogs, beware of evil workers, beware of the concision." (Phil. 3:22Beware of dogs, beware of evil workers, beware of the concision. (Philippians 3:2)). "Without are dogs, and sorcerers, and whoremongers, and murderers, and idolaters, and whosoever loveth and maketh a lie." (Rev. 22:1515For without are dogs, and sorcerers, and whoremongers, and murderers, and idolaters, and whosoever loveth and maketh a lie. (Revelation 22:15)).
The Lord would not put Christians in a class with dogs and other evil workers, such as whoremongers and murderers. Dogs in the East are very different creatures from the valued companions of men in these countries. These pariah dogs are wild and dangerous, belonging to no one, and devouring what scraps of garbage they can find in the dusty road. In Scripture they are only symbolic of evil.
And as to the sow please note, at best it is only a washed sow, a sow still, with a sow nature, that loves wallowing in the mire. Surely Scripture would not liken a Christian to a sow, washed though it might be. We read of believers being likened to the sheep of Christ, but never to a sow.
This Scripture brings before us the condition of mere professors, who naturally may go back to their old sinful ways, seeing there is no inward reality to restrain them.
At the first Christianity made such an impact upon Judaism and the pagan world that many unbelievers attended the gatherings of the Christians, and doubtless were influenced for a time for good, but having no inward reality, no vital touch with God, such were liable to backslide, in which case it were better for them never to have known the way of righteousness than to turn away from it. Such are described as the dog returning to his vomit, and the washed sow to her wallowing in the mire.