For whatever it's worth, Cameron143, and if you don't mind me commenting, the word "dog" in itself is representative/symbolic of the unsaved - it wasn't just arbitrarily chosen by God in Pet 2:22 to be standalone - it has biblical spiritual significance extending beyond that verse. By the verse stating they "turned" to their own vomit, even after having gained a knowledge of Christ, it means they then returned back from whence they had come - that they were dogs (unsaved) before gaining the knowledge, and they returned to it after gaining the knowledge - they were still dogs - they had never become changed by God from being dogs (unsaved) spiritually or they wouldn't have returned back to it- they remained unchanged and in that same spiritual state. They gained knowledge through natural man's earthly abilities but not though a spiritual mind; that is to say, that no spiritual conversion for them had occurred - they were never made saved/born again.
I think we can gain some insight from these verses in that the Bible generally uses the word "dog" spiritually as representative of the unsaved:
[Psa 22:20 KJV] 20 Deliver my soul from the sword; my darling from the power of the dog.
[Rev 22:14-15 KJV]
14 Blessed [are] they that do his commandments, that they may have right to the tree of life, and may enter in through the gates into the city.
15 For without [are] dogs, and sorcerers, and whoremongers, and murderers, and idolaters, and whosoever loveth and maketh a lie.
This is already probably already obvious to you, but I thought that I'd mention it anyway.