Just a few thoughts attempting to encapsulate the Bible's overall teaching about assurance.
1. There are both true and false believers in the visible church
2. Some false believers have a false assurance
3. Some true believers lack assurance
4. True believers CAN have full assurance in Christ from “day 1″ of their conversion.
5. We can’t tell FOR CERTAIN whether a fellow professing Christian is a true or false believer
6. We must test ourselves to be sure we aren’t self-deceived.
7. We must encourage and provoke our brothers so that if they are self-deceived it will come to light and they can repent unto true belief and thus gain assurance.
I believe there is Scriptural support for each statement. But is anything missing or misguided in my list?