How Certain Can You Be?

When your friend asks you to prove the existence of God, ask him to prove that his wife loves him.

Proving the existence of God is a strange task, along the lines of proving that my wife loves me. However, we are called upon to do it from time to time by our non-Christian friends. “How can you be so certain?” they ask. “What if you’re just imagining it all? How can you prove to me that this God of yours exists?”

The key to proving God’s existence is selecting the right kind of proof. For our purposes here, we need to distinguish between three types of certainty or proof:

  • absolute certainty;
  • reasonable certainty;
  • personal certainty.

Absolute certainty exists only in the world of mathematics and logic. It is built on ‘deductive’ reasoning-that is, coming to a logical conclusion from a set of premises. For example, if all men are made of cheese, and Socrates is a man, then it follows irresistibly that Socrates is made of cheese. This is absolutely certain provided, of course, that the original premises are true. Absolute certainty based on deductive argument begs the question of the soundness of the premises.

Reasonable certainty is the level of proof we use most often in day to day life. It is based on ‘inductive’ reasoning-that is, weighing pieces of evidence and drawing a general conclusion. For example, swan number one is white; swan number two is white; and swan number three is white. From this evidence, we might draw the general conclusion that all swans are white, but since we do not have absolute knowledge (that is, knowledge of all swans everywhere) there will always be an element of uncertainty. There may be some swans somewhere that are black. The incomplete nature of our knowledge means that this sort of certainty can only be ‘reasonable’ or ‘probable’ rather than absolute.

This is the kind of certainty we use in regard to historical events and, therefore, in court. A jury is asked to decide ‘beyond reasonable doubt’, on the basis of the evidence, whether a particular event happened (e.g. whether a man committed a particular crime). Similarly, in analysing an historical event (such as the resurrection of Jesus), we can only say with reasonable certainty that it happened. We weigh the evidence and draw a conclusion. To demand absolute, mathematical certainty for the resurrection of Jesus is unreasonable and inconsistent. We treat no other event or person in this way-why should Jesus be an exception?

However, there is a third level of proof, which we might call personal certainty, that exists in personal relationships. Our knowledge of persons goes beyond ‘reasonable certainty’. Our relationship with them gives a kind of knowledge that is more profound than simply weighing evidence and coming to a conclusion.

For example, how do I know that my wife loves me? I could cite evidence of loving things she has done, and her manner towards me, and that she says that she loves me. I do not have absolute certainty, because I do not have absolute knowledge. However, there is a key factor-I have a relationship with my wife that the disinterested questioner does not share. Our history of shared experience and conversation builds a sense of personal certainty that goes beyond simply weighing evidence and coming to a conclusion.

This is similar, in many ways, to our relationship with God. Our friendship with God consists of more than a cold, analytical weighing of the evidence. As we get to know him, and understand him, and see him at work in our lives, our assurance grows. It outstrips the ‘reasonable certainty’ of weighing the evidence for Jesus’ resurrection.

When we are asked, then, to ‘prove’ the existence of God, we need to make sure that we talk about the right kind of ‘proof’.

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