What is the second death?
The second death is the lake burning with fire and brimstone, which is the final separation from God. The fearful, unbelieving, abominable, murderers, whoremongers, sorcerers, idolaters, and law liars have their part in it. It is the portion of those not in the eternal state.
Les explains that the second death is the lake burning with fire and brimstone, which he identifies as the final separation from God. In the recap of verse 8, he notes this is a reminder of who will not be in the eternal state with believers: the fearful, unbelieving, abominable, murderers, whoremongers, sorcerers, idolaters, and law liars. This follows the promise that he who overcomes shall inherit all things and be God's son, contrasting eternal inheritance with final separation.
But the fearful, and unbelieving, and the abominable, and murderers, and whoremongers, and sorcerers, and idolaters, and all liars, shall have their part in the lake which burneth with fire and brimstone: which is the second death.