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Sources of Knowledge

Xuanzang & the Gettier Problem

Maya Koka journeys through the desert to seek knowledge about knowledge.

The date is 632 AD. The location is Lanzhou, China. The time is precisely 10:00 am. A Buddhist monk named Xuanzang and his companion, a tiger, are journeying through the Gobi Desert. Their mission: to find water. Suddenly they see a valley resembling a blue expanse. Xuanzang turns to his feline friend and remarks, “Look, there is water!” Unfortunately, the glistening blue is a mirage. Yet, when they reach the valley, Xuanzang finds water, hidden beneath a large rock. Did the Buddhist monk know there was water ahead? In other words, is his initial belief that there was water in the valley to be considered knowledge?

This situation of Xuanzang’s represents what philosophers these days call a Gettier case. This is a philosophical problem made famous by Edmund Gettier (1927-2021) in an attempt to critique the traditional Socratic or Platonic theory of knowledge as being ‘justified true belief’. On that account, having a belief that is both justified and true is necessary and sufficient for knowledge. If one has a justified true belief, one has knowledge. However, while justified true belief is indeed a necessary conditions for knowledge, Gettier showed that it is not sufficient. He did this by giving various instances in which an agent has a belief both true and justified, yet which fails to be knowledge. I want to look at a novel formulation of the Gettier problem, and also consider a method to respond to Gettier cases through the instantiation of a fourth condition for knowledge.

First, how can we know that we have any knowledge at all? Let’s once again revisit 632 AD. According to the justified true belief model, Xuanzang has knowledge of there being water in the valley based on the following conditions:

a) Xuanzang is justified in believing there is water in the valley because he perceives a blue hue which he registers as water.

b) Xuanzang believes there is water in the valley.

c) Xuanzang finds water there, so it is true there is water there.

Here ‘justification’ refers to evidential support – such as Xuanzang’s recognition of the blue hue as water. Socrates and later philosophers posited the justification condition to safeguard knowledge claims against luck. A lucky guess doesn’t count as knowledge since there is no good reason to believe it is true.

Xuanzang looking for water 14th C. anon.

However, it seems that although Xuanzang’s belief was true, this was a lucky coincidence, and not a result of his inference from seeing a blue haze in the valley. Gettier spurred widespread philosophical debate by presenting cases of accidental occurrences of true belief, demonstrating that the idea of knowledge as justified true belief cannot ensure against luck (originally in his brief paper ‘Is Justified True Belief Knowledge?’, Analysis, 1963). I won’t discuss Gettier’s own cases, but I will apply his findings to Xuanzang. Can Xuanzang’s initial claim to knowledge be ruled out by his finding water being simply luck?

There is no doubt that it is a matter of luck he finds water, as there is no causal relationship between Xuanzang thinking he sees water ahead and his actually finding water. But without a causal relationship between there being water ahead and his belief that there is water ahead, that belief cannot be an instance of knowledge. This underlines the idea that the conditions stated in ‘justified true belief’ are necessary rather than sufficient for knowledge, since knowledge requires more than a belief accidentally being proven correct. Therefore, in response to Gettier cases, several contemporary epistemologists have developed a fourth condition for knowledge: that the truth of a belief must be non-accidental. Theorists such as Alvin Goldman would argue that Xuanzang would only have knowledge if there were a causal connection between his belief that there is water and the fact that there is water (see ‘A Causal Theory of Knowing’, Journal of Philosophy, 1967, 64:12). For Goldman, Xuanzang’s initial belief is not knowledge precisely because although it is true and justified, it is not causally connected to the fact that there actually is water. Specifically, when Xuanzang ‘sees’ water, he is not seeing water, and especially not the water that he will soon find. For this reason, such thinkers argue that belief causality should form the basis of knowledge.

This causal theory of knowledge is well-intentioned, of course, but it is not exempt from flaws. According to Grefte and Gebharter in ‘The Causal Theory of Knowledge Revisited: An Interventionist Approach’ (Ratio, 2021, 34:3), even if an individual’s belief is causally connected to the truth formulated by the belief, it is still possible for the believer to lack knowledge. For example, let’s suppose that Xuanzang does not see a mirage ahead, but instead sees a real body of water. Let’s also suppose that due to local climatic conditions in Lanzhou there are numerous mirages, which do not contain any water but from a distance are indistinguishable from real water. By chance, Xuanzang is presently looking at the only genuine lake in Lanzhou. For Goldman, Xuanzang’s belief would count as knowledge, because it is caused by there actually being a body of water ahead. Yet we can plausibly assert that Xuanzang’s belief does not actually qualify as knowledge because it arises out of epistemic luck. If he had been looking at one of the many mirages instead, his belief would have been false. There is, therefore, reason to reject a simple causal theory of knowledge for the same reason we rejected justified true belief, namely its inability to ensure against accidental occurrences.

So even justified true belief plus the causal theory of knowledge fail to sufficiently define knowledge. Yet although Xuanzang never attained knowledge in his journey through the Gobi Desert, his quest marks an illuminating shift in epistemology. Too often, Gettier cases are viewed as philosophical diamonds, unanimously favored in contemporary debates. But the story of Xuanzang illuminates a complex tension between knowledge and epistemic luck, bringing us one step closer to realizing what it means to truly know.

Maya Koka is a Foundation Scholar studying philosophy in the International Dual BA program between Columbia University and Trinity College Dublin.