The theory of justification is a part of epistemology that attempts to understand the justification of propositions and beliefs. Epistemologists are concerned with various epistemic features of belief, which include the ideas of justification, warrant, rationality, and probability. Loosely speaking, justification is the reason that someone (properly) holds a belief.

When a claim is in doubt, justification can be used to support the claim and reduce or remove the doubt. Justification can use empiricism (the evidence of the senses), authoritative testimony (the appeal to criteria and authority), or reason.

Theory of justification is a part of epistemology that attempts to understand the justification of propositions and beliefs. Epistemologists are concerned with various epistemic features of belief, which include the ideas of justification, warrant, rationality, and probability. Of these four terms, the term that has been most widely used and discussed by the early 21st century is “warrant”. Loosely speaking, justification is the reason that someone (properly) holds a belief.

When a claim is in doubt, justification can be used to support the claim and reduce or remove the doubt. Justification can use empiricism (the evidence of the senses), authoritative testimony (the appeal to criteria and authority), or logical deduction.

Justification is the reason why someone properly holds a belief, the explanation as to why the belief is a true one, or an account of how one knows what one knows. In much the same way arguments and explanations may be confused with each other, as may explanations and justifications. Statements which are justifications of some action take the form of arguments. For example attempts to justify a theft usually explain the motives (e.g., to feed a starving family).

It is important to be aware when an explanation is not a justification. A criminal profiler may offer an explanation of a suspect’s behavior and such statements may help us understand why the person committed the crime. An uncritical listener may believe the speaker is trying to gain sympathy for the person and his or her actions, but it does not follow that a person proposing an explanation has any sympathy for the views or actions being explained. This is an important distinction because we need to be able to understand and explain terrible events and behavior in attempting to discourage it.

During the past two or three decades, justification has become a central topic in epistemology. The interest in justification grew out of the attempts to give the correct analysis of knowledge in the face of the famous counterexamples given by Edmund Gettier to the so-called traditional conception of knowledge in his 1963 paper. The interest in knowledge may have decreased, but the disputes about the right account of justification go on more vigorously than ever. Indeed, there are at present so many distinct theories of epistemic justification advocated by different disputants that it makes one doubt whether they are actually talking about the same thing at all. Before considering these theories, we shall therefore make first an attempt to locate the common concept or property that they are all theories of.

We need some pretheoretic understanding of the target concept or property if we are to evaluate the different theories. It is often assumed that we already possess such an understanding because we have all learnt the language to which the term ‘justification’ belongs. That is why we have intuitions about the applicability of the concept that we can use to test the theories. However, it is far from clear that there is any ordinary concept of epistemic justification. The term ‘epistemically justified’ does not have such a customary use in ordinary language as the term ‘to know’, as William Alston (1989, p. 5) has pointed out. And even if there were such a concept, many epistemologists would not seem to be interested in it. ‘Justification’ is a term of art in epistemology.

This makes it even more important to try to identify the concept of justification we are interested in. Unfortunately, there is no unanimity among epistemologists about how to do this. There are at least three different ways of characterising our target concept. All these characterisations need not be incompatible. However, if they motivate competing theories about the substantive conditions of justification, they must be understood as descriptions of distinct concepts. Indeed, the most permanent and fundamental disagreements about the substantive issues become understandable when different conceptions of justification are seen to motivate them. We must therefore acknowledge that there are several distinct concepts of justification and that some competing theories of justification are not actually in conflict at all but are theories about different matters.1

I will divide this presentation into two parts that are often called meta-epistemology and substantive epistemology. Meta-epistemology is concerned with the central concepts of epistemology, such as knowledge and justification, trying to give, if not a complete analysis, at least some kind of description of their content. The task of substantive epistemology is to apply these concepts to different kinds of beliefs, trying to determine what knowledge and justified beliefs we have. With respect to justification, this is done by formulating epistemic principles that specify the conditions under which various beliefs qualify as justified. The distinction may also be put by saying that while meta-epistemology is concerned with the nature of justification, substantive epistemology tries to specify the criteria of justification.

I will start by looking at those three conceptions of justification and discuss the most important substantive theories after that. Because I will conclude that there are different concepts of cpistcmic justification in circulation, I will end up by considering what kind of concept or concepts of justification we need in epistemology. This requires that we think over what is the point of having a concept of justification at all. What is the purpose for which we need it? So I will finally address the question concerning the nature of epistemology itself. What is its proper task and what are its most important questions?

Justification and Knowledge

In the Theaetetus dialogue, Plato raises the question ‘What distinguishes knowledge from true belief?’ According to a view that has been popular at least in the twentieth century, the answer is justification. Knowledge is true and justified belief in this view, which is often called the traditional conception of knowledge. It is sometimes even attributed to Plato who suggests in Meno (98a) that what turns true belief into knowledge (episteme) is the possession of an account {aitias logismos) — working out of an explanation. However, for Plato, this account seems to be rather an answer to the question ‘What is XT than to the question ‘How do you know that pT It is the latter question that is taken by contemporary philosophers to be the central question of epistemology and to which the proper answer is to give a justification for believing that p. So it is, at best, controversial to say that Plato himself accepted the traditional conception or analysis of knowledge.2

Be the historical truth what it may, it is at least true that several epistemologists in the last century have advocated the traditional analysis of knowledge. They have thought that knowledge is something more than a lucky guess. A belief that is true by accident is not knowledge. What is required is justification. If we accept this, we get a characterisation of justification: it is something that turns true belief into knowledge. The concept of justification can therefore be understood in terms of truth, belief and knowledge. This is appropriate, because justification seems to be the least understood of these four concepts. Theories of justification would thus be answers to the question Plato raises in Theaetetus: what distinguishes knowledge from true belief?

Things are not quite so simple. Edmund Gettier (1963) showed by two counterexamples that the traditional analysis of knowledge is not correct: true and justified belief is not sufficient for knowledge. In spite of this, most epistemologists go on taking justification to be a necessary condition of knowledge. What must be done is to add some fourth condition to the traditional analysis to rule out Gettier’s original and other similar counterexamples. So most philosophers who have written about epistemic justification in the last forty years have taken it for granted that justification is something that is required for knowledge and that at least contributes to making true belief knowledge.

It is often argued that if justification is to distinguish knowledge from an accidentally true belief, it must be truth-conducive. A justified belief must be probably true. After Gettier, this argument has lost some of its force.