Irrefutable Scepticism? The Agrippan Trilemma

Everyone is, apparently, sceptical in some way shape or form, whether one is sceptical of certain political promises, of the validity of a certain newspaper or of the authenticity of a piece of artwork, it can be said that everyone has their doubts. However, this form of scepticism should perhaps be regarded as ordinary incredulity rather than true scepticism in the philosophical sense. Regarding the latter, various epistemologies, although not founded in scepticism, still pertain of scepticism to a degree; a rationalist could be said to be sceptical about empirical knowledge, and vice versa, an empiricist would remain sceptical of all knowledge apriori. Indeed, true philosophical scepticism rests on propositions which cannot be verified as is the nature of scepticism as first proposed by Socrates,“I know nothing except the fact of my ignorance”, whereas ordinary incredulity can be removed by verification through finding the truth of some further proposition of the relevant type. For the sake of clarity, I would quote Wittgenstein; “A doubt without an end is not even a doubt.”

Having examined one form of scepticism in my previous article on Underdeterminism, we now turn our attention to the Agrippan Trilemma which, if correct, poses a threat to all theories of knowledge on a much broader scale. The Agrippan Trilemma was first formulated by Agrippa, the sceptic circa (1st century A.D.). Best known for his writings on the “Five tropes of doubt”, he propagated the idea that all knowledge was based on flawed grounds, fivefold due to relativism, epistemic dissent, progression ad infinitum, circularity and axiomatic assumption, with the latter trio consisting the Trilemma. In this article, we shall examine the logical claim that this argument makes and subsequently, question its validity.

The Argippan Trilemma has foundation in the principle of sufficient reason, as stated by Leibniz, which asserts that everything must have reason or cause why it is so. Hence, the Trilemma challenges any claim to knowledge repeatedly so until one of three outcomes are reached:

  1. The claim progresses ad infinitum
  2. The claim relies on circular reasoning
  3. The claim is based on axiom

Purportedly, all these outcomes are flawed. Concerning (1), infinite regression essentially does not admit of a first principle and thus, an endless regress of reason will not satisfy the claim to knowledge as subsequent question must be asked of given reasons ad infinitum. The argument based on (2) is equally weak because it relies on apriori reason to support aposteriori reason and vice versa. Thus, there is no order of reasons as such since both reasons are dependent on the other for recourse to explanation. With regards (3), it simply claims, of no logical reason, to halt the regression of sufficient reason at an arbitrary axiom. The whole argument is based upon untenable assumption. Therefore, all three horns in the Agrippan Trilemma end in fallacious fashion, and it seems that all knowledge per se is rendered inconclusive, or rather, fundamentally founded on illogical grounds.

To relate the Trilemma to modern epistemologies, we can clearly see of which illogical ground they are based on; with ‘infinitism’ purporting of (1) – based upon ad infinitum claims, advocates of ‘coherentism’ founding episteme on (2) – condoning reciprocal reasoning, and ‘foundationalists’ clearly leaning on (3) – basing knowledge upon arbitrary axiom.

However, the foundationalist, chief of whom was Descartes, would make conjecture in that they would claim axioms foundational to knowledge in fact contain the principle of sufficient reason intrinsically in their composition. Hume said of this (although Hume was by no means a foundationalist); that the sufficient reason for a whole was the sum of its parts. Thus, there is no need of external recourse for explanatory reason. Certainly in light of this, the foundationalist would claim that such axioms as the cogito are justified per se, intrinsically, perhaps with regards their “clear and distinct” conception.

Perhaps, a more convincing counter argument is one that turns the Agrippan Trilemma on its head, asking of itself the same question that it asks of all knowledge – why must this be so? Indeed, it is seen that the impossibility to prove of a certain truth is not, ironically, a certain truth. Intrinsically, for the Agrippan Trilemma to appertain conviction, it must have recourse to some axiomatic logical principles so no justification for the Trilemma can seemingly be given. Therefore, it seems that unless the sceptic would make exception to the rule, the Trilemma seems to refute itself at consummation. However, the sceptic would here so to speak, “bite the bullet”, in that although the Agrippan Trilemma is false of itself, it still has inevitable effect on all epistemology as thereof endorsing similar logical principles.

In the final analysis, unless epistemic exception can be found that passes the Trilemma, complete scepticism lingers as no claim is logically justified.

Contributed by Tim Livingstone

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