If you read my previous controversial post on certainty and salvation, you now need to read Clark’s post on his own blog which responds with an opposing argument. Here’s the link explaining why you can be certain of your salvation:
If you need the tl;dr version, here’s his conclusion (but I encourage you to read the whole thing):
In quick summary, the existence of the mind can be shown to be properly basic, meaning, a self-evident axiom. Reason is not separable from the mind. God exists, firmly dispelling the evil genius hypothesis. If the Bible is divine revelation, which, barring some incontrovertible opposing reason, it certainly is, then it is characteristic of God. If something is characteristic of God, then it is certain. Therefore, one can be certain of personal salvation.