The regress argument (or infinite regress argument) is an argument in epistemology. It is closely related to the Problem of the criterion and is often presented by skeptics as a refutation of the belief that humans can know anything with certainty.

Table of contents
1 The argument
2 Responses to the argument
3 Circularity
4 Coherentism
5 Foundationalism

The argument

The regress argument is essentially an observation of the dialectic. Any time a person asserts that a given proposition is true, that proposition can be questioned as to its truth by asking, "Why do you believe that proposition to be true?" If the person who originally stated the proposition provides reasons, each of these reasons can be similarly questioned. This questioning could theoretically regress infinitely, if the asserter of truth were creative enough to continue to produce arguments into infinity.

The predictable outcome is that eventually the asserter of truth is reduced to making statements like, "That is just the way it is." Or, "Everyone believes this so you can't question it." Or, "If you don't believe THAT then you are crazy or insane." Or, "Foundationalism proves that this is true." Eventually, most people when faced with continual un-ending questioning arrive at basic beliefs that they believe are fundamental and do not require an explanation. The Skeptics questions about these foundational beliefs sound crazy. It sounds like they are asking, "How you know that reality is reality?" That is precisely the question they are asking. It is a difficult question to answer. Philosophers have been trying to answer it since Pyrrho.

This back and forth process of asserting truth and requesting a justification for believing it is the backbone of the discipline of Philosophy. It is difficult for any person to say when and where this questioning should end. Any such claim on absolute truth sounds like dogma to the skeptic.

Responses to the argument

(1) Suppose that the belief P is justified by the belief P'; so P' justifies P.

(2) But if P' is to be a satisfactory justification for P, then P' must also be justified.

(3) So P' is justified.

(4) But if P' is justified, then it must be justified by some other belief, and that belief must be justified by some other belief, and so on. Thus, there is a chain of justifying beliefs.

And then there are three possibilities:

(a) the chain goes on forever
(b) the chain loops around on itself, forming a circle
(c) the chain begins with a belief that is justified, but which is not justified by another belief.

(5) Possibility (a) (called regressism) is logically incorrect because there must be a beginning reason.

(6) Possibility (b) (a naive version of coherentism) is logically incorrect for reasons explained below.

(7) Possibility (c) (called foundationalism) is the only possibility left and must be logically correct.

(8) Therefore, there must be some beliefs that are justified, but which are not justified by other beliefs: these are called basic beliefs. All other beliefs are justified by basic beliefs.

Thus the regress argument is an argument for a theory of justification called foundationalism.

A more in detail description claims that the regress argument advances the idea that if a belief is justified by another belief, then the justifying belief itself must be justified. Premise 4 is the really important step of the argument: "If P is justified, then it must be justified some other belief; and that belief must be justified by some other belief; and so on. There is a chain of justifying beliefs. And then there are three possibilities: (a) the chain goes on forever; (b) the chain loops around on itself, forming a circle; or (c) the chain begins with a belief that is justified, but which is not justified by another belief."

Therefore, for any belief that P is justified by P' requires that some fact justifies P', and that something justifies that, ect. Since an infinite number of justifying beliefs is logically impossible, there must be another choice. One possibility is that the belief justifies itself, either directly (P justifies P) or indirectly (P justifies P' which justifies P" which justifies P). The whole set of beliefs then forms a circular chain of justification. Another possibility is that P is not justified by a belief but by something else.

Premises 5 and 6 eliminate options a and b, respectively, leaving only option c as a logical possibility. Premise 5 claims that a chain of justification can not go on forever.

Circularity

Another possibility from premise (4) is that the chain of justification loops around on itself, forming a circle. That is essentially what happens in a coherent system of mutually supporting beliefs. An example is that:

  1. I believe that we are at Ohio State
  2. I believe that University Hall is on the Ohio State campus
  3. I believe that I have seen many papers, booklets, and other materials indicating that I am a philosophy instructor at Ohio State
  4. I believe I am seeing you all right now in front of me, and that you are students; moreover, I believe you are Philosophy 101 students, and that I am your teacher; and so on.
These beliefs are mutually supporting, meaning that the belief that I am teaching you Philosophy 101 supports the belief that I have seen many materials indicating that I am a philosophy instructor; and vice-versa, the belief that I am a philosophy instructor supports the belief that I am teaching you Philosophy 101.

Coherentism

Coherentism is the belief that an idea is justified iff it is part of a coherent system of mutually supporting beliefs (i.e., beliefs that support each other). In effect Coherentism denies that justification can only take the form of a chain. Coherentism replaces the chain with a holistic approach.

The most common objection to naive Coherentism is that it implies that circular justification is acceptable. Meaning that in this view, P ultimately supports P, which is not an acceptable form of reasoning; this logical error is called begging the question. Coherentists reply that it is not just P that is supporting P, but P along with the totality of the other statements in the whole system of belief.

Another issue about Coherentism is that it accepts any belief that is part of a coherent system of beliefs. In contrast, P can cohere with P' and P" without P, P' or P" being true. To respond that the system of beliefs has to be derived from experience in reality would be to replace Coherentism with a form of foundationalism. Instead, Coherentists might say that it is very unlikely that the whole system would be both untrue and consistent, and that if some part of the system was untrue, it would almost certainly be inconsistent with some other part of the system.

A third objection to Coherentism is that some beliefs arise from experience and not from other beliefs. An example is that one is looking into a room which is totally dark. The lights turn on momentarily and one sees a white canopy bed in the room. The belief that there is a white canopy bed in this room is based entirely on experience and not on any other belief. Of course, possibilities exist, such as that the white canopy bed is entirely an illusion or that one is hallucinating, but the belief remains well-justified. Coherentists might respond that the belief which supports the belief that there is a white canopy bed in this room is that one saw the bed, however briefly. This appears to be an immediate qualifier which does not depend on other beliefs, and thus seems to prove that Coherentism is not true because beliefs can be justified by concepts other than beliefs. However the experience of seeing the bed is indeed dependent on other beliefs, about what a bed, a campy and so on, actually look like.

Foundationalism

Foundationalism is the belief that a chain of justification begins with a belief that is justified, but which is not justified by another belief. Thus, a belief is justified iff:
  1. it is a basic/foundational belief (i.e., it is justified by a non belief), or #it is justified by a basic belief or beliefs
  2. it is justified by a chain of beliefs that is ultimately justified by a basic belief or beliefs.

An analogy to explain this idea compares foundationalism to a building. Ordinary individual beliefs occupy the upper stories of the building; basic, or foundational beliefs are down in the basement, in the foundation of the building, holding everything else up. In a similar way, individual beliefs, say about economics or ethics, rest on more basic beliefs, say about the nature of human beings; and those rest on still more basic beliefs, say about the mind; and in the end the entire system rests on a set of beliefs, basic beliefs, which are not justified by other beliefs, but instead by something else.

Foundationalism seeks to escape the regress argument by claiming that there are some beliefs for which it is improper to as for a justification.

Beliefs are basic iff it is justified, but it is not justified by other beliefs. This requiers that sensory perception justify basic beliefs. Others claim that an event of perception can begin a chain of belief. An objection to this idea is that a hallucination can cause an event of perception without corresponding to reality.

Foundationalists support their idea by claiming that sense experience can be a belief in itself. For example, suppose that one claims that one had fallen and scraped one's knee as a child. With not witnesses or other records, there is no fact which can support this belief except that one remembers it. In effect, the belief that one scraped one's knee is supported by one's memory of having scraped one's knee. This begs the question of what makes one believe that one is justified in believing this sensory memory. Ultimately, then, this sensory belief is justified by another belief, that one's memory is reliable and true.