Agrippa’s Trilemma and the Positions of Infinitism, Coherentism and Foundationalism

The Thinking Lane
5 min readMar 3, 2023

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Know more about the ancient Pyrrhonean trilemma that puts the grounds of justification for beliefs into question

Introduction to Agrippa’s Trilemma

The Agrippan Trilemma was a mode of argument which was used by the ancient Pyrrhonean skeptics to point out the flaws in the arguments of those who believed that they had used reasoning to determine the truth or falsity of something. It was used as a tool to suspend judgement.

Who was Agrippa?

Agrippa was a Pyrrhonean skeptic philosopher who lived during the last decades of the 1st century CE. He has been attributed with putting forward “The Five Tropes of Agrippa”. The source of this is Sextus Empiricus’ work “Outlines of Pyrrhonism”.

What is Agrippa’s Trilemma About?

Agrippa pointed out that for any Q, one has no reason to believe that Q is justified. He explained this through five modes, three of which became known as Agrippa’s Trilemma.

The Five Modes and the Trilemma

Following are Agrippa’s five modes:

  1. Dissent — Uncertainty exists because of a difference in opinions among individuals
  2. Progress ad infinitum — Infinite regress problem arises because proofs for a thing themselves require proofs, infinitely
  3. Relation — Things change as the perspective of looking at them changes
  4. Assumption — An unsupported assumption is at the foundation of the truth being asserted
  5. Circularity — Circular chain of reasoning is involved while asserting a truth

Since the first and the third modes were already introduced by Aenesidemus in the first century BC, and only the other 3 showed advancement in Pyrrhonist skepticism, they came to be known as Agrippa’s Trilemma.

Agrippa’s Trilemma — Why and How Does It Arise?

We hold a number of beliefs that we think are justified. To list a few, we might think that it is justified to believe that -

  1. The sun is a star.
  2. Something cannot come from nothing, so God created the universe.
  3. Venom is poisonous.

As has been generally accepted, knowledge is justified, true belief. Hence, justification is a necessary condition for classifying something as knowledge. But if one is asked to justify any of the three beliefs listed above, or any other that they think they know to be true, they are faced with three undesirable options.

Option #1

They admit that their belief is unsupported. The sun is a star. Why? It just is.

Option #2

They admit that their belief is supported by an infinitely long chain of justifications. Something cannot come from nothing, so God created the universe. Who created God? A divine entity preceding God. Who created that? An even earlier divine entity… (and so on till infinity).

Option #3

They admit that their belief is supported by a circular chain of justifications. Venom is poisonous. Why? Because it harms the person with whom it makes contact. Why? Because it is poisonous.

None of these three options provides a valid justification for holding beliefs. They all seem intuitively wrong. This can be further clarified with the analogy of a house. A house is not well-supported if it has: 1) no foundation 2) an unending chain of foundations 3) a circular foundation

Other Similar Trilemma/Issues

In Indian philosophy, a similar problem is described in Nāgārjuna’s Vigrahavyāvartanī. German philosopher Hans Albert’s Münchhausen-Trilemma describes a similar concept. In Karl Popper’s Logic of Scientific Discovery, it is claimed that it was Jakob Friedrich Fries who first came up with this trilemma (which Popper called Fires’ Trilemma).

Three Replies To The Trilemma and their Criticism

Regressive Argument

This is regarded as the least popular and plausible response to the trilemma. As per the regressive argument (alternatively known as the position of infinitism), the second option, i.e., the one that claims that a belief can be supported by an infinitely long chain of justifications — is right.

Critics argue that they are unable to see how this could be the case — given how the mere idea of there being an infinite chain of justifications is counterintuitive. Defenders of infinitism argue that aside from the counter-intuitiveness of this position, there is no reason for infinitism to not be correct.

Circular Argument

This response is more popular than the regressive argument. The position of Coherentism claims that the third option, i.e., the one that claims that a belief can be supported by a circular chain of reasoning — is right.

Supporters of this view claim that if the circle of justifications is big enough, it can provide adequate supporting grounds for a belief. This approach is generally used for a number of our beliefs that are part of a web of beliefs supporting each other (which can be called our worldview). Our beliefs form our worldview, which further generates beliefs.

Critics of this view argue that even though this approach is generally used, that does not make it right. Implicitly appealing to the web of beliefs one has in order to justify a belief is not a sound approach as it falls prey to the fallacy of begging the question. In short — just because we have a tendency of forming beliefs in a particular way, does not mean that that tendency is right.

Dogmatic Argument

It might not seem that way at first, but the dogmatic argument or the position of foundationalism is the most popular one. As per this position, a belief can be justified without being supported by further beliefs. This means resorting to the first option, i.e., that one does not require further supporting beliefs to hold a belief. Proponents of the classical form of foundationalism claim that this is the case because there are some beliefs that are self-justifying and hence do not require any justification outside of themselves.

Descartes is a popular foundationalist. He claimed that the belief in one’s existence is a foundational belief, which is infallible. So any chain of justification with this belief at its foundation would be justified.

Critics of this view point to the lack of such infallible, self-justifying foundational beliefs. Such a small number of beliefs would not be able to serve as foundations for a majority of the beliefs that we hold. Defenders of this view might argue that the requirements of foundational beliefs could be loosened up to accommodate more beliefs into the pool — but such a loosening would admit some fallible beliefs, defeating the aim of having an infallible foundation.

Endnote and Conclusion

It is thus made clear how none of these three responses to Agrippa’s Trilemma offers a satisfactory way out of it. One way to make the trilemma disappear is to remove justification as a necessary criterion for knowledge. But that would mean that one is entitled to possess beliefs without having a reason to do so. This approach, not unlike the three explained above, is counterintuitive.

That being said, Foundationalism seems to be the most desirable way out of the Trilemma as it has, in its support, Descartes’ convincing epistemological contributions.

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The Thinking Lane
The Thinking Lane

Written by The Thinking Lane

Hi! I am Kritika Parakh. I am a philosophy grad trying to make sense of philosophical topics. Any criticism/corrections/comments are welcome.

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