by John M. Frame

[“Certainty,” for IVP Dictionary of Apologetics.]


Certainty is a lack of doubt about some state of affairs. For example, if I have no doubt that the earth is the third planet from the sun, then I can be said to be certain of that fact. Certainty admits of degrees, just as doubt admits of degrees. Absolute certainty is the lack of any doubt at all. Short of that, there are various levels of relative certainty.

Philosophers have sometimes distinguished between psychological certainty, which I have described above, and another kind of certainty that is called epistemic, logical, or propositional. There is no universally accepted definition of this second kind of certainty, but it usually has something to do with the justification or warrant for believing a proposition: a proposition is epistemically certain if it has, let us say, a maximal warrant. The nature of a maximal warrant is defined differently in different epistemological systems. Descartes thought that propositions, to be certain, must be warranted such as to exclude all grounds for doubt. For Chisholm, a proposition is epistemically certain if no proposition has greater warrant than it does. And different philosophers give different weight to logic, sense experience, intuition, etc. in determining what constitutes adequate warrant.

In my judgment, epistemic certainty, however it be defined, is not something sharply different from psychological certainty. Whatever level of warrant is required for epistemic certainty, it must be a level that gives us psychological confidence. Indeed, if we are to accept some technical definition of warrant, we also must have psychological confidence that that definition actually represents what we call certainty. So it may be said that epistemic certainty is reducible to psychological certainty. But it is also true that we should try to conform our psychological feelings of certainty to objective principles of knowledge, so that our doubts and feelings of certainty are reasonable, rather than arbitrary or pathological. So perhaps it is best to say that psychological and epistemic certainty are mutually dependent. In Frame, Doctrine of the Knowledge of God, I have tried to describe and defend the mutual reducibility of feelings and knowledge.

Philosophers have also differed as to the extent to which certainty is possible, some being relatively skeptical, others claiming certainty in some measure. Some have distinguished different levels of knowledge and have relegated certainty to the higher levels. Plato, for example, in the Republic, distinguished between conjecture, belief, understanding, and direct intuition, conjecture being the most uncertain, and direct intuition (a pure knowledge of the basic Forms of reality) warranting absolute certainty.

Is it possible to be absolutely certain about anything? Ancient and modern skeptics have said no. According to Descartes, however, we cannot doubt that we are thinking, and, from the proposition ‘I think,’ he derived a number of other propositions that he thought were certain: our existence, the existence of God, and so on. Empiricists, such as Locke and Hume, have argued that we cannot be mistaken about the basic contents of our own minds, about the way things appear to us. But in their view our knowledge of the world beyond our minds is never certain, never more than probable. Kant added that we can also be certain of those propositions that describe the necessary conditions for knowledge itself. And Thomas Reid and G. E. Moore argued that certain deliverances of common sense are beyond doubt, because they are in some sense the foundation of knowledge, better known than any principles by which they can be challenged.

Ludwig Wittgenstein distinguished between merely theoretical doubt and real, practical doubt. In everyday life, when we doubt something, there is a way of resolving that doubt. For example, when we doubt how much money we have in a checking account, we may resolve that doubt by looking at a check register or bank statement. But theoretical, or philosophical doubts are doubts for which there is no standard means of resolution. What would it be like, Wittgenstein asks, to doubt that I have two hands, and then to try to relieve that doubt? Similarly for doubts as to whether the world has existed more than five minutes, or whether other people have minds.

The language of doubt and certainty, Wittgenstein argues, belongs to the context of practical life. When it is removed from that context, it is no longer meaningful, for meaning, to Wittgenstein, is the use of words in their ordinary, practical contexts, in what he calls their language game. To raise such philosophical questions is to question our whole way of life.  Thus for Wittgenstein, relative certainty is possible in ordinary life through standard methods. But the traditional philosophical questions are not proper subjects either of doubt or of certainty.

So in the context of ordinary life Wittgenstein allows for certainty of a relative kind. His argument evidently excludes absolute certainty; but he does recognize some beliefs of ours (e.g. that the universe has existed for more than five minutes) about which there can be no doubt. He excludes doubt, not by proposing an extraordinary way to know such matters, but rather by removing such questions from the language game in whichdoubt and certainty have meaning.

But philosophy is also a language game, and doubts about the reality of the experienced world have troubled people for many centuries. Philosophers have not hesitated to propose ways of resolving those doubts. So it may be arbitrary to restrict the meanings of doubt and certainty to the realm of the practical, even given the possibility of a sharp distinction between theoretical and practical. At least it is difficult to distinguish between questions that are improper in Wittgenstein’s sense and questions that are merely difficult to answer.

So the questions concerning certainty remain open among secular philosophers. Since Wittgenstein, these questions have been raised in terms of foundationalism, the view that all human knowledge is based on certain ‘basic’ propositions. Descartes is the chief example of classical foundationalism, because of his view that the basic propositions are absolutely certain. Many recent thinkers have rejected foundationalism in this sense, but Alvin Plantinga and others have developed a revised foundationalism in which the basic propositions are defeasible, capable of being refuted by additional knowledge. In general, then, the philosophical trend today is opposed to the idea of absolute certainty; and that opposition is rampant among deconstructionists and postmodernists.

The question also arises in the religious context: can we know God with certainty? The Bible often tells us that Christians can, should, and do know God and the truths of revelation (Matt. 9:6, 11:27, 13:11, John 7:17, 8:32, 10:4-5, 14:17, 17:3, many other passages). Such passages present this knowledge, not as something tentative, but as a firm basis for life and hope.

Scripture uses the language of certainty more sparingly, but that is also present. Luke wants his correspondent Theophilus to know the ‘certainty’ (asphaleia) of the things he has been taught (Luke 1:4) and the ‘proofs’ (tekmeria) by which Jesus showed himself alive after his death (Acts 1:3). The centurion at the cross says ‘Certainly (ontos) this man was innocent’ (Luke 23:47, ESV).

The letter to the Hebrews says that God made a promise to Abraham, swearing by himself, for there was no one greater (6:13). So God both made a promise and confirmed it with an oath, ‘two unchangeable things, in which it is impossible for God to lie’ (verse 18). This is ‘a sure and steadfast anchor of the soul’ (verse 19). Similarly Paul (2 Tim. 3:16-17) and Peter (2 Pet. 1:19-21) speak of Scripture as God’s own words, which provide sure guidance in a world where false teaching abounds. God’s special revelation is certain, and we ought to be certain about it.

On the other hand, the Bible presents doubt largely negatively. It is a spiritual impediment, an obstacle to doing God’s work (Matt. 14:31, 21:21, 28:17, Acts 10:20, 11:12, Rom. 14:23, 1 Tim. 2:8, Jas. 1:6). In Matt. 14:31 and Rom. 14:23, it is the opposite of faith and therefore a sin. Of course, this sin, like other sins, may remain with us through our earthly life. But we should not be complacent about it. Just as the ideal for the Christian life is perfect holiness, the ideal for the Christian mind is absolute certainty about God’s revelation.

We should not conclude that doubt is always sinful. Matt. 14:31 and Rom. 14:23 (and indeed the others I have listed) speak of doubt in the face of clear special revelation. To doubt what God has clearly spoken to us is wrong. But in other situations, it is not wrong to doubt. In many cases, in fact, it is wrong for us to claim knowledge, much less certainty. Indeed, often the best course is to admit our ignorance (Deut. 29:29, Rom. 11:33-36). Paul is not wrong to express uncertainty about the number of people he baptized (1 Cor. 1:16). Indeed, James tells us, we are always ignorant of the future to some extent and we ought not to pretend we know more about it than we do (James 4:13-16). Job’s friends were wrong to think that they knew the reasons for his torment, and Job himself had to be humbled as God reminded him of his ignorance (Job 38-42).

So Christian epistemologist Esther Meek points out that the process of knowing through our earthly lives is a quest: following clues, noticing patterns, making commitments, respecting honest doubt. In much of life, she says, confidence, not certainty, should be our goal.

But I have said that absolute certainty is the appropriate (if ideal) response to God’s special revelation. How can that be, given our finitude and fallibility? How is that possible when we consider the skepticism that pervades secular thought? How is it humanly possible to know anything with certainty?

First, it is impossible to exclude absolute certainty in all cases. Any argument purporting to show that there is no such certainty must admit that it is itself uncertain. Further, any such argument must presuppose that argument itself is a means of finding truth. If someone uses an argument to test the certainty of propositions, he is claiming certainty at least for that argument. And he is claiming that by such an argument he can test the legitimacy of claims to certainty. But such a test of certainty, a would-be criterion of certainty, must itself be certain. And an argument that would test absolute certainty must itself be absolutely certain.

In Christian epistemology, God’s word is the ultimate criterion of certainty. What God says must be true, for, as the letter to the Hebrews says, it is impossible for God to lie (Heb. 6:18, compare Tit. 1:2, 1 John 2:27). His Word is Truth (John 17:17, compare Ps. 33:4, 119:160). So God’s word is the criterion by which we can measure all other sources of knowledge.

When God promised Abraham a multitude of descendants and an inheritance in the land of Canaan, many things might have caused him to doubt. He reached the age of one hundred without having any children, and his wife Sarah was far beyond the normal age of childbearing. And though he sojourned in the land of Canaan, he didn’t own title to any land there at all. But Paul says of him that ‘no distrust made him waver concerning the promise of God, but he grew strong in his faith as he gave glory to God, fully convinced that God was able to do what he had promised’ (Rom. 4:20-21). God’s word, for Abraham, took precedence over all other evidence in forming Abraham’s belief. So important is this principle that Paul defines justifying faith in terms of it: ‘That is why [Abraham’s] faith was counted to him for righteousness’ (verse 22).

Thus Abraham stands in contrast to Eve who, in Gen. 3:6, allowed the evidence of her eyes to take precedence over the command of God. He is one of the heroes of the faith who, according to Heb. 11, ‘died in faith, not having received the things promised, but having seen them and greeted them from afar…’ (verse 13). They had God’s promise, and that was enough to motivate them to endure terrible sufferings and deprivations through their earthly lives.

I would conclude that it is the responsibility of the Christian to regard God’s word as absolutely certain, and to make that word the criterion of all other sources of knowledge. Our certainty of the truth of God comes ultimately, not through rational demonstration or empirical verification, useful as these may often be, but from the authority of God’s own word.

God’s word does testify to itself, often, by means of human testimony and historical evidence: the ‘proofs’ of Acts 1:3, the centurion’s witness in Luke 23:47, the many witnesses to the resurrection of Jesus in 1 Cor. 15:1-11. But we should never forget that these evidences come to us with God’s own authority. In 1 Cor. 15, Paul asks the church to believe the evidence because it is part of the authoritative apostolic preaching: ‘so we preach and so you believed’ (verse 11; compare verses 1-3).

But how does that word give us psychological certainty? People sometimes make great intellectual and emotional exertions, trying to force themselves to believe the Bible. But we cannot make ourselves believe. Certainty comes upon us by an act of God, through the testimony of his Spirit (1 Cor. 2:4, 9-16, 1 Thess. 1:5, 2 Thess. 2:14). The Spirit’s witness often accompanies a human process of reasoning. Scripture never rebukes people who honestly seek to think through the questions of faith. But unless our reason is empowered by the Spirit, it will not give full assurance.

So certainty comes ultimately through God’s word and Spirit. The Lord calls us to build our life and thought on the certainties of his word, that we ‘will not walk in darkness, but have the light of life’ (John 8:12). The process of building, furthermore, is not only academic, but ethical and spiritual. It is those who are willing to do God’s will that know the truth of Jesus’ words (John 7:17), and those that love their neighbors who are able to know as they ought to know (1 Cor. 8:1-3).

Secular philosophy rejects absolute certainty, then, because absolute certainty is essentially supernatural, and because the secularist is unwilling to accept a supernatural foundation for knowledge. But the Christian regards God’s word as the ultimate criterion of truth and falsity, right and wrong, and therefore as the standard of certainty. Insofar as we consistently hold the Bible as our standard of certainty, we may and must regard it as itself absolutely certain. So in God’s revelation, the Christian has a wonderful treasure, one that saves the soul from sin and the mind from skepticism.



J. M. Frame, Doctrine of the Knowledge of God (Phillipsburg, N. J.: 1987).

E. L. Meek, Longing to Know: the Philosophy of Knowledge for Ordinary People (Grand Rapids, MI: 2003).

A. Plantinga, Warranted Christian Belief (N. Y.: 2000). A profound Christian reflection on the nature of knowledge and its warrant.

L. Wittgenstein, On Certainty (N. Y., 1972).

W. J. Wood, Epistemology (Downers Grove, 1998). Christian philosopher shows how knowledge is related to virtues and to the emotions.


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