Tijdschrift voor filosofie
sinds 1969


Caught in Agrippa's grip

Bryan Beeckman

Can we have knowledge and if so, how can we acquire it? These are questions that have captivated the interest of philosophers, especially epistemologists, for ages. The Traditional Analysis of Knowledge (TAK) holds that we can indeed have knowledge.  According to this theory, one has knowledge if and only if one has a justified true belief (i.e. a belief that is justified and true). In 1963, Edmund L. Gettier successfully challenged the traditional definition of knowledge by postulating solid cases in which one has a justified true belief but still does not have knowledge. Although Gettier has  indicated that justification is not a sufficient condition for knowledge, it is still a necessary one. Yet, justified true belief as a necessary condition for knowledge raises further questions: can a belief be justified? If so, how can it be justified? These questions need to be addressed! If we cannot answer these questions adequately, we might end up in the arms of scepticism and have to concede, although it has an unnatural feel to it, that we cannot have knowledge at all. But before sliding into scepticism, let us remain in a positive and hopeful mindset and examine a theory that has tried to specify the theory of justification, i.e. foundationalism.

Foundationalism: saving knowledge by means of basic beliefs
The founding father of foundationalism is the French philosopher René Descartes. On the basis of his reasoning in his Meditations on First Philosophy, epistemologists have constructed the Cartesian or classical foundationalist theory of justification. This theory holds that some beliefs are justified by themselves (i.e. they are self-justifying) because we cannot be mistaken about these beliefs. Thus, basic beliefs are infallible beliefs. Cartesian foundationalists argue that our own inner states of mind (e.g. how things of the external world feel, look, smell and taste) and beliefs about logic can be regarded as basic beliefs. The rest of our beliefs, concerning the external world, can be deduced from these basic beliefs and are, consequently, justified by them. The implication of these self-justified basic beliefs is that they put an end to the chain of reasons and thus we do not end up in a regressus ad infinitum.

However, critics have postulated some objections against the Cartesian view of basic beliefs. One of the most striking arguments against Cartesian foundationalism is that the majority of our beliefs cannot be deduced from basic beliefs of our inner states of mind or of logic. The deductive argument is simply too restrictive, leading us to have knowledge of just a few things. 

In reaction to critiques of Cartesian foundationalism, modest foundationalists will argue that beliefs can be justified by basic beliefs without being deduced from them. Moreover, they also drop the infallibility argument. According to them, basic beliefs are perceptual beliefs about the external world which are justified but not immune to error. These beliefs can also be spontaneous, non-inferential beliefs. However, basic beliefs of this kind must also be a response to one’s experiences and not be defeated by the evidence one has at that time. Thus, compared to Cartesian foundationalism, modest foundationalists provide a broader set of basic beliefs because basic beliefs (1) do not have to be infallible and (2) can also be beliefs about the external world.

Since modest foundationalism broadens the definition of a basic belief critics view it as a bit too liberal compared to Cartesian foundationalism. Moreover, modest foundationalism needs to answer some serious questions, for example: if our justified basic beliefs can also be fallible, how can they function as justified basic beliefs? Allowing fallible beliefs to function as basic beliefs would make the justification theory to be based on unstable ground (instead of the desired solid ground). It seems that some beliefs are unsupported and cannot be justified at all, an argument also made by sceptics. This would lead us to believe that basic beliefs are non-existent. Is the sceptic right after all?

Agrippa’s trilemma: no justification, no knowledge
One of the sceptics of justification is the Pyrrhonian philosopher Agrippa who lived around 100 AD. Agrippa’s trilemma is widely known among epistemologists as one of the most challenging arguments concerning justification. If one wants to know more about Agrippa’s trilemma, one should look at the description of the arguments in the two extant primary sources: Diogenes Laërtius’ Lives of Eminent Philosophers and Sextus Empiricus’ Outlines of Pyrrhonism. In these texts we find five modes of scepticism attributed to Agrippa. However, only three of them are known as Agrippa’s trilemma:

(1) Every proof requires a fresh proof in endless regress;
(2) Proof presupposes unproved premises;
(3) Proof involves a circular argument.

Thus, when someone claims to know a proposition p, the sceptic might ask what kind of reasons (or justification) that person has for knowing p. Consequently, that person might give a reason R to justify his knowledge of p. However, the sceptic will then ask what reason(s) one has for R. This question can be answered in a threefold way:

  1. By constantly giving a new reason for the aforementioned reason, e.g. R1 is justified by R2, R2 is justified by R3, R3 is justified by R4, etc. 

  2. By giving several reasons and stopping at a certain reason explaining that this reason eventually justifies all other reasons: e.g. R1 is justified by R2, R2 is justified by R3.

  3. By giving reasons until a certain point where an aforementioned reason is re-used to justify another: e.g. R1 is justified by R2, R2 is justified by R3, R3 is justified by R1.

This first answer leads to a regressus ad infinitum. However, since we are bound to our human existence (which is finite), we cannot come up with infinite reasons in order to justify a certain belief. The second argument also creates problems. When we state that a certain reason is not justified but it does justify other reasons, why do we stop in providing reasons? If we can sufficiently answer this question then we have already given another reason and we start a new chain of reasons which can eventually also lead to a regressus ad infinitum. However, if we cannot answer this question, then our last reason might seem to be arbitrary and we might end up in dogmatism. The last answer is also problematic. When referring to a previously given argument in order to justify a new argument, we end up in circular reasoning. This would mean that several reasons are also justified by themselves.

As ought to be clear from the above, on the basis of Agrippa’s trilemma the sceptic can argue that if knowledge requires justified true belief we cannot have knowledge at all since our beliefs cannot properly be justified. It seems that Agrippa has us in his grip. The sceptic dooms us to believe that we cannot acquire knowledge. 

Both the traditional form as well as the modest form of foundationalism try hard to find their way out of the Agrippan trilemma by providing an adequate account of justification based upon the mode of Agrippa that states that proof must not presuppose unproved premises. However, as we have seen above, both theories fall short in providing a solid theory of justification. The sceptic prevails!

It appears that there is no clear-cut answer to the Agrippan problem. Perhaps, for now, we can acknowledge that the problem cannot be resolved by any particular theory of justification. Therefore, we remain stuck in Agrippa’s grip. I leave it to the reader to judge whether this is a good or a bad thing…