Sextus Empiricus: Ancient Epistemology and the Fuzziness of Truth

by Matthew Pike
Ph.D. Student, CU Boulder

§ Abstract

Given the key role that our experiences of the world play in our knowledge formation, a successful argument against the reliability of these experiences would serve to force us to accept some version or other of skepticism. Advocating this skeptical result, and the tranquility he believes will ensue in its wake, the Roman philosopher and physician Sextus Empiricus (C. 160-210 AD) presents several arguments in his Outlines of Skepticism intended to undercut our faith in the accuracy of our perceptions and experiences of the external world.  In one of the more interesting of these arguments, Sextus claims that the variation in the appearances that different animals receive of the world entails that we cannot be confident that our experiences of the external world are veridical. More specifically, variations in the structure and function of the sense organs and sensory-information processing centers responsible for the impressions (or, as we might prefer to think of them, informational representations) that an organism receives about the world will result in some corresponding variation in the content of those impressions. Given that different species do have observable differences in their sensory and cognitive systems, they will have (potentially drastically) different perceptions and experiences of the world, where identical objects will yield different appearances. If what is experienced can differ by species, then, according to Sextus, we could not be confident that our experiences as humans are veridical, unless some method of determining that we are experiencing and perceiving the external world accurately could be found.  This paper will evaluate the strength of this argument, and then consider what seems to be the most plausible response to it—that the more complex cognitive abilities that humans possess provide reason to not only prefer the perceptions of humans as more accurate than those of other animals, but also justify us in believing that we are getting at the world as it really is. This response, however, will ultimately be shown to be inadequate for addressing Sextus’ worries.

 

§ Introduction

Given that many or,  if one favors a strict empiricist approach, all of our candidates for knowledge are based at least partly upon our experiences of the world, a successful argument against the reliability of these experiences would serve to force us to accept some version or other of skepticism. Advocating this skeptical result, and the tranquility he believes will ensue in its wake, Sextus Empiricus presents several arguments in his Outlines of Skepticism intended to undercut the Dogmatists’ faith in the accuracy of their perceptions and experiences of the external world.  In one of the more interesting of these arguments, Sextus claims that the variation in the appearances that different animals receive of the world entails that we cannot be confident that our experiences of the external world are veridical. This paper will evaluate the strength of this argument, and then consider what seems to be the most plausible response to it—that the more complex cognitive abilities that humans possess provide reason to not only prefer the perceptions of humans as more accurate than those of other animals, but also justify us in believing that we are getting at the world as it really is. This response, however, will ultimately be shown to be inadequate for addressing Sextus’ worries.

§ Establishing the Variables
Sextus provides several reasons to accept that different animals perceive and experience the world in different ways, but this portion of his argument can be adequately established using only one of the approaches on offer. Sextus observes that, “it is reasonable that external existing objects should be observed as different depending on the different constitutions of the animals receiving the appearances” (Sextus, I. 54, p.16) and that, “it is the differences among the most important parts of the body, especially those which are naturally fitted for deciding and perceiving, which can produce the greatest conflict of appearances” (Sextus, I. 44, p.14). In other words, variations in the structure and function of the sense organs and sensory-information processing centers responsible for the impressions (or, as we might prefer to think of them, informational representations) that an organism receives about the world will result in some corresponding variation in the content of those impressions. 1 Given that different species do have observable differences in their sensory and cognitive systems, they will have (potentially drastically) different perceptions and experiences of the world, where identical objects will yield different appearances.

If what is experienced can differ by species, then, according to Sextus, we could not be confident that our experiences as humans are veridical, unless some method of determining that we are experiencing and perceiving the external world accurately could be found.  However, as Sextus says

if the same objects appear dissimilar depending on the variation among animals, then we shall be able to say what the existing objects are like as observed by us, but as to what they are like in their nature we shall suspend judgement. For we shall not be able ourselves to decide between our own appearances and those of other animals, being ourselves a part of the dispute and for that reason more in need of someone to decide than ourselves able to judge. (Sextus, I. 59, p.17)

Without direct access to the objective “fact of the matter”, it seems that we can neither compare our perceptions to those of other animals and determine which is more accurate, nor establish that any animal’s impressions are veridical. It is a fundamental limitation of our experiential situation that, because our understanding of the external world originates in our perceptions, we cannot ever be sufficiently removed from our subjective experience to objectively evaluate its correspondence to the truth. This restricts us to speaking of what Kant later calls the phenomenal world, and serves to make attempted claims about the noumenal world impossible (as anything but mere speculation, anyway).

§ A Rational Response?
Do these variations in appearances really doom us to Pyrrhonism?  Not necessarily. As Annas and Barnes note

[t]he mere citation of conflicting appearances may not suffice to induce skepticism. Sextus plainly feels that we may respond to it not by skepticism but by an affirmation that the conflict is decidable – we can prefer one set of appearances, perhaps human appearances, to any other. (Annas and Barnes, 1985, p.50)

The most plausible approach to refuting Sextus’ argument would seem to make use of the greater cognitive abilities that humans possess to try to establish that we are in a position to judge between different, potentially conflicting, appearances. One might argue that because our brains conserve much of the “primitive” functionality found in the brains of other animals (for example, the brainstem found in human brains is structurally and functionally similar to that found in amphibians, cats, primates, etc), but also possess a much larger cerebrum, we are capable not only of the base kind of perception that other animals have, but also of more advanced cognitive processes that can provide methods of detecting and discovering the external world accurately.

Our abilities to remember and compare conflicting perceptions in order to better discover a consistent view about the entity that caused them, as well as our ability to formulate experiments for the express purpose of researching the entities in question (perhaps making use of tools and instruments that we have designed for these purposes) and to make various kinds of inferences that entail further information about the world all may be seen as giving us good reason to think that we are successfully getting at the world “as it is”. Additionally, our linguistic abilities allow us to engage in complex communication with other members of our species and incorporate their perceptions, experiences and conclusions, increasing both the sample set from which we draw our inferences, and comparing the results from our investigations. Even the very notion of an objective truth which might differ from our immediate experience and drives us to try to be attentive to unusual sensory conditions, inconsistent appearances, and fallacious reasoning seems to give humans a distinct advantage when it comes to discovering truth. It is also arguable that our immense scientific success in manipulating various aspects of the natural world provides strong reason to believe that our mental representations of the world do correspond (at least very closely) to objective reality (see Psillos, 1999 for a good example of this line of argumentation). Some of these lines have been discussed further in the philosophical literature on various realist approaches to epistemology, and so we will here restrict the discussion to this sketch of how this response might go, and turn to evaluating how well this type of approach may work against Sextus’ argument.

§ Animals All
While these complex cognitive abilities that humans possess may make it seem more probable that humans are capable of discerning facts about the actual world, there are two responses a skeptic can utilize to demonstrate that this response is inadequate.

First, even if one accepts that our perceptions of the world are accurate, this view, combined with our best scientific theories, will entail a commitment to evolution that undermines the solution on offer. The sensory and cognitive systems that humans and other organisms possess are taken to result from the continued mutation and natural selection processes of evolution. While this process provides a good account of why we have systems that allow us to function in the surrounding environment, there is no reason to believe that the evolutionary process yields systems that reliably track truth. After all, evolution selects for traits that increase an organism’s ability to survive long enough to reproduce, but there may be cases where it is pragmatic to perceive or believe things that do not correspond to the fact of the matter. For example, the biologist Richard Dawkins sometimes describes our perception as being of the “middle world”- we directly perceive objects on the scale of tables and chairs, not on the scale of individual molecules or galaxies. It is useful to our survival as “middle-sized” organisms to perceive other objects that are close to us in size. But this level of perception yields appearances that differ drastically from the subatomic particles picture that our best physical theories suggest is a more accurate representation of reality. So, while our sensory systems and enhanced cognitive abilities yield representations that are generally “good enough” for survival purposes, there is not a further step available to establish their veridicality.

Additionally, different animals, if they are still existent at this time, have demonstrated an equally successful ability to survive in the surrounding environment. If this is what perception and informational representation are aimed at and selected for, different animals may be seen as having an equal claim to the truth of the matter.

Second, as Sextus points out, any reason we have for holding that we are more rational or more cognitively developed than other animals will itself be based on the perceptions and experiences we have of the world, and so simply begs the question at issue. 2. Indeed, it seems that most animals could not possibly have the perception that we are more rational than they are, and so will necessarily have different perceptions of this situation. Unless we can find a way of reformulating the realist response on offer that does not utilize sense data or cognitive processing, or a way of independently establishing their reliability that does not make use of either of them (which seems unlikely, if not impossible in principle), this approach cannot be taken to address the worries that Sextus has put forth.

§ Conclusion

These two skeptical responses demonstrate that the argument from the variation among animals should still be seen as threatening to anyone who wishes to hold that our appearances about the external world are veridical and can serve as the basis for knowledge. While the concern about whether we can know that our impressions correspond to the objective “fact of the matter” could arise even if there were no known variations in appearances, having conflicting variations exist between different perceivers experiencing the same reality necessitates that at least some of these experiences and perceptions are inaccurate (unless we are willing to abandon a correspondence notion of truth and move to relativism, of course). Without a guaranteed way of reliably differentiating which perceptions are accurate and which are not, the epistemic situation looks grim for both dogs and Dogmatists.


§ Bibliography

 Annas, Julia and Johnathan Barnes, The Modes of Skepticism: Ancient Texts and Modern Interpretations. New York: Cambridge University Press, 1985.

 Sextus Empiricus, Outlines of Skepticism. Tr. J. Annas and J. Barnes, Cambridge, Cambridge University Press, 2000.

 Psillos, Stathis, Scientific Realism: How Science Tracks Truth. New York: Routledge, 1999

 Van Fraassen, Bas, Laws and Symmetry. Oxford: Clarendon Press, 1989.

1. One could be tempted to resist this claim, but it is worth noting that not only do our best neuro-scientific theories strongly support this conclusion, but also that every contemporary view of the nature of mental experience (with the exception of idealism, which would need to be argued for independently) conceives of the sensory system as a physical system (governed by physical causation) that will yield different outputs if it’s structure is sufficiently altered. Animals without eyes are not able to see, and animals with different sensory organs will be able to perceive different things than we do (consider, for example, the infrared vision that some snakes possess, the echo-locating ability of bats, and the ability of some organisms to naturally detect magnetic fields). We also know that some animals lack the necessary rod and cone structures in their eyes to be able to perceive the same color spectrum as we do, and that some organisms can see ultraviolet light that we cannot. These are just a few examples of variation that biologists tell us exist in the world, and seem to convincingly establish a correlation between sensory-system composition and experience.

2. Sextus may have another possible response to this line of argumentation available: he could try to deny that we are in fact more rational and in the possession of additional cognitive abilities that animals do not have, and so are not in a sufficiently privileged epistemic position. As he says, if animals “fall short of humans neither in the accuracy of their senses nor in internal reasoning nor (saying this for good measure) in expressed reasoning, they will be no less convincing in respect of the appearances than we are” (Sextus,  I.76, p.21). Sextus attempts (somewhat humorously) to demonstrate that an animal such as a dog meets the key criteria that the Dogmatists put forth in this area, but we may simply choose to reject this particular criteria and instead put forth a more specific, psychologically or neuro-scientifically grounded cognitive measure that does adequately differentiate between species’ cognitive abilities.

 

Matt Pike

8/20/17: Time for the new semester! Materials for PHIL1200 Fall 2017 are posted in the Courses/Teaching section.

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