The most famous "doubter" in the Bible is the apostle Thomas - commonly described as "doubting Thomas". He simply could not believe in the resurrection of Jesus. The other disciples came to believe, but not Thomas. Why was that? John's Gospel supplies the answer. It was "because he was not with them when Jesus came" (John 20.24). Thomas kept himself apart from the other disciples. He was absent when the risen Jesus appeared to them.
This is still a fundamental cause of doubt - a person's separation from the Christian community or fellowship. If you keep away from where the Bible is intelligently and carefully preached, if you don't put yourself in the way of Christian literature that is positive and helpful, if you don't let other Christians help you with your queries and questions, don't be surprised if you find faith difficult.
John Wesley used to say that there is no such thing as a "solitary Christian". Charles Spurgeon used the analogy of the coal in the fire. While the coal is in the fire it glows hot. Take it out and lay it on the hearth and it grows cold. The Christian is like the coal.
When we are outside an active Christian fellowship, it is so easy to drift from the faith. C.S.Lewis once observed:
"If you examined a hundred people who had lost their faith in Christianity, I wonder how many of them would turn out to have been reasoned out of it by honest argument? Do not most people simply drift away?"
Sadly, you see this happen to a number of people in churches. The "worries of this life" as Jesus put it in the Parable of the Sower (Mark 4.19), often are all that is needed to start a drift. This then leads to a creeping paralysis of faith.
This happened to Charles Darwin (the evolutionist):
"I gradually came to disbelieve in Christianity as a divine revelation ... disbelief crept over me at a very slow rate, but was at last complete."
The devil in Lewis's The Screwtape Letters puts it so well:
"The safest road to Hell is the gradual one - the gentle slope, soft underfoot, without sudden turnings, without milestones, without signposts."
There is also undue scepticism. That is not at all uncommon. There are some people who are always asking for evidence but are never open to conviction.
The Pharisees in the New Testament were just like that (and their successors are still with us). Jesus called them "a wicked and adulterous generation" (Matthew 12.39). They were always asking for a "sign". But they had signs enough. As Peter could say without fear of contradiction in his Pentecost sermon: "Jesus of Nazareth was a man accredited by God to you by miracles, wonders and signs" (Acts 2.22).
But many of the Jews simply did not want to submit to Jesus Christ as Saviour and Lord. It was a question of the "will", not the intellect.
There are, of course, real doubts. As Os Guinness puts it:
"This is the point at which to separate those who are doubting because they need answers from those who are doubting because they need doubts."
One real problem people have from time to time is over the nature of proof. "How", they ask, "can you be really sure? Yes, the arguments given are very good, but can we be certain?"
The trouble often begins when we do not have a wide enough idea of what it means to "prove" something. Too often we think exclusively of "mathematical" proofs. Or we think of "logical" proofs, where the meanings of the words almost ensure that a conclusion is right. "All men are mortal; Socrates is a man; therefore Socrates is mortal."
But that is only one sort of proving. We mustn't be held prisoner by it. There are all sorts of other ways we prove things. For example a Romeo proves his love for a Juliet in countless ways that have nothing to do with mathematical or logical proofs.
There is a range of methods by which we reach certainty - enough certainty. The important thing is to ask yourself two questions: "Am I looking for the appropriate sort of proof?" and "Am I aware of what is a reasonable amount of certainty for action?"
The simple fact is that in everything apart from what philosophers call "necessary truths" - mathematical and logical truths - there is no such thing as "absolute certainty of a mathematical sort". So what? Indeed, this is what makes life interesting. And this is particularly true of human relationships. You only become certain about people as you get to know them. As Michael Green has well said: "The appropriate way to assure yourself of the reality of persons is to meet them, not to try to prove them."
The Christian says it is a bit like that with the risen Jesus Christ. The more you have dealings with him and the more you develop a relationship with him, the more certain you become. That is not to say that Christians don't have questions and sometimes doubts. But they are sufficiently certain. This is not about everything. In many things "now we see but a poor reflection as in a mirror" (1 Corinthians 13.12). However, over the essentials they are sufficiently certain to be able to love, serve and obey God.
Some people will still doubt that Christian "proving" and certainty is reasonable. They will put Christian believing in much the same class as a toss of a coin - heads I win, tails you lose. It's a matter of chance. Alan Watts once said: "Without disrespect it must be said that Christianity is pre-eminently the gamblers' religion."
It was the 17th century Frenchman, Pascal, who originally used the analogy of "gambling" in thinking of faith. He taunted the sceptics of his own day, who doubted the existence of God and the resurrection of Jesus Christ, over their reckless gambling habits. They were prepared, he said, to stake huge fortunes in their gambling with far less chance of being winners or proved right in their bets than are Christians in their beliefs.
Pascal certainly didn't mean, however, that Christian belief was merely a "luckier" draw. He used the analogy of gambling to emphasise commitment. His point was this:
"We cannot wait until our reason has carefully weighed all the pros and cons, the less so since the existence of God can never be proved by reason alone. In the meantime we waste our life in indecision ... Let us take the risk, therefore, let us boldly dare to believe, even though merely on the strength of a vague probability."
The point is well made (even if we think that the probability is not vague but high). Practical decisions can't wait for ever. And a decision to accept and follow Jesus Christ is a practical decision. It is going his way and not ours. We will do different things if we are Christians to what we will do if we are not.
In many areas of life you cannot remain uncommitted for ever. Sometimes you have to "jump". And even in situations where the evidence is strong and clear, you can always carry on asking questions to avoid commitment.
Imagine a rather odd person - odd because he wants 100 percent certainty - on a station platform. He wants to know when is his next train home. He asks the porter who tells him, "5.00 pm". But he wants to make sure; after all the porter may have got it wrong. So he goes back to the booking office and sees the official timetable. There it is - 5.00 pm. However, he thinks: "that might be a misprint" or "they might have changed the schedules today. I better check with the stationmaster." While doing so, he looks at his watch. It now says, 5.01 pm. He looks back to the platform and there he sees the train slowly pulling away. He has missed it.
In practical situations you cannot remain uncommitted for ever. And you cannot remain uncommitted to Jesus Christ for ever. He is coming again!