Ian,
There are people--and even some pastors--who
very foolishly advise their hearers to look to themselves and their performance to obtain a measure of assurance that they are "making it," that they are saved.
But this is damaging counsel. It is possible for practically anyone to take some encouragement from his deeds, and comfort himself that it looks to him like spiritual life and growth. And because anyone
can do it, and there's no objective measure of the "quality" of the work, such a measure is unreliable and formally and practically useless.
-- Person One has lived as a Christian for, say, 20 years, and thinks he has quantified, objective measures of his spiritual "improvement" over that time. He is pretty sure he can tell that he is at least 51% better than he was. He's a very disciplined person, and tithes of his money and his time to charitable causes and to his church.
-- Person Two has lived as a Christian for, say, 30 years, and seriously wonders if he has made any measurable "progress" spiritually in all that time. His prayer life has gone up and down. He thinks he has more self-control in one area, but less in another. He loves his three children more, but his wife less. He's more aware of his sin than he's ever been.
Which one of these men is more assured of his place in the kingdom of heaven? Just based on the information above, there is NO POSSIBLE way to tell. They can't tell themselves, nor can others tell. These descriptions might even be the same man, ten years apart!
The way to assurance is to look
away from yourself. Like Peter who obeyed the summons of Christ to walk on the waves with him, we are fine when we keep our eyes on Jesus, not on our own feet (natural ability) or on the winds and waves (earthly circumstances). Peter's confidence could NEVER be in his own act of walking. Each step further couldn't, shouldn't, wouldn't make him more confident in himself. Only looking to Jesus kept him upright.
Scripture tells us that believers really do grow in grace. The Spirit of Christ who dwells in his people is the Spirit of obedience (inverse Eph.2:2), the Spirit who cries out "Abba, Father," Gal.4:6. These are statements by God that believers should embrace. Children, who only see life stretching out interminably in front of them may think they will never grow up; they cannot tell from day to day that they have advanced at all. But their parents confidently tell them, "O, you certainly will grow up." And the children should believe them.
I just preached through 1Cor.8. One of the problems in Corinth was spiritual pride: the confidence folks had in their spiritual attainments in knowledge, deeds, and giftedness. Paul describes two parallel spiritual ideals of the Christian life, knowledge and love. Knowledge without love is puffed up, empty and vain. Love is knowledge in action. Without knowledge, love is useless activity without any direction. So each ideal is dependent on the other.
Paul points out, v2, that no one yet knows anything spiritually as he ought, not even the person who knows the most. So, it is impossible to gauge one's spirituality by testing one's knowledge; because if we always ought to be better knowers than we are, then we don't know "enough" to escape blame.
Well, what about the other ideal? What about love? Can I measure my spirituality--my knowledge of God--by how much love I show? After all, love is the working out of knowledge, the building up of good, of others... What does the Apostle say? Does v3 read, "If you love God (a little/a lot), then clearly you know God (a little/a lot)?"
No, v3 surprises the reader by subverting "my love" as an index to "my knowledge" of God, as an index to "my spirituality." A new believer who has very little knowledge may show forth his (new) love for God in ways that put the long-term believer, who may know much more, in the shade (for a variety of reasons). Rather, v3 reads, "If anyone [thinks he] loves God, [let him take comfort only in this:] that he is KNOWN BY God." Let that Christian remember this: that "we love him because he first loved us," 1Jn.4:19.
Do you think you love God? Good, but don't take comfort in such feelings or displays. Think only of how whatever love is there is purely the product of a prior divine act of love toward you.
How do you know you have faith? How do you know you are alive, bodily? Is it because you measure your breaths? Is it because you are constantly taking your pulse? Is it because you ran to the store this morning? What if you are a brain in a vat? Radical skepticism can undermine every confidence, if you give it free reign.
How do you know if you have faith? Do you believe the Word of God, or don't you? Do you know it, accept it as true, and rest in it? That's faith.