“Now faith is being sure of what we hope for” (Hebrews 11:1). But how sure does ‘sure’ have to be? 50% sure? 90%? Will only 100% certainty be sufficient? Jesus tells us that even faith as small as a mustard seed can move mountains. Actions are the evidence/proof of faith – but it isn’t necessary to be 100% sure of something before committing yourself to a course of action. If that were the case, we’d never do anything.
Alister McGrath has written an excellent little book on the subject of doubt, in which he makes the point that doubt is an integral part of Christian faith. Certainty, perhaps surprisingly, is the opposite of faith. “We walk by faith, not by sight” (II Corinthians 5:7): God hasn’t revealed absolutely everything to us, but He has revealed enough for us to trust Him (Deuteronomy 29:29). It is that trust which enables us – not to resolve our doubts completely, but to learn to live with them.
Most Christians experience fluctuating degrees of assurance about their faith (if you are an exception, then I salute you). But it is the dependability of God’s Word that assures us of our salvation, not the variable feeling of certainty that we experience. “Faith is basically the resolve to live our lives on the assumption that certain things are true and trustworthy, in the confident assurance that one day we will know with absolute certainty that this is indeed the case.” (A McGrath: Doubt)
Discovering the Bible 