In the unbeliever, introspection leads to despair as the sinner recognizes his sin, or to presumption if he believes he has obeyed the law, or to utter contempt of the law which condemns him.

The believer has been liberated from the bondage of the law. Introspection leads him to reflect on his many and great sins. The believer does not look for the assurance of salvation based on his own imperfect obeidance but in the promise of the gospel which the Holy Spirit causes him to believe and keeps him in that faith.

So I was quite shocked when I read Mr. Thomas Brooks and others urge an assurance of salvation based on a subjective examination of one's fruits. Can you explain?