by Alexander Earl
How do we know what we know? Do we even know anything? What does it mean to know something, anyhow? Come to think of it, how do you know you’re not dreaming, that these words are not a figment of your imagination, or that you’re not hallucinating? It may seem an odd question at first, but I’m sure you’ve experienced dreaming an entirely vivid dream with the force of reality; what makes you so certain that your entire experience is not that way? If you’re honest, you find yourself being wrong about all kinds of things, so what has you feeling so secure about your dearly held beliefs and opinions, or your basic assumptions about daily life? You often seem quite sure that other people have gotten things wrong, so why should it be any different with you? These sorts of questions inevitably crop up in some form in an introductory philosophy class, and they are the kinds of questions that are certain to irritate and frustrate some of the participants. Sometimes that vexation affirms the assumption that philosophy is an inherently useless endeavor with no ‘real-world’ value. I once taught a philosophy of religion class in a parish setting that had a rather gritty and elderly gentleman in the back exclaim how absolutely pointless the whole endeavor was: we know we’re not dreaming because we know we’re not dreaming! We need to be pragmatists! The pleasure of a black-eye will surely wake you from your worthless philosophical musings!
But one shouldn’t get too worked up over such instances—and, admittedly, I may be exaggerating—if Socrates is any indication, it has been the reaction to philosophy from the very beginning, so the philosopher should know what they are getting themselves into before inquiring heedlessly; however, one can also have hope that there are many others who will find the exercise positively beguiling and enthralling. For the hopeful latter, consider further my gritty elder, there is something philosophically fascinating in his frustration and his consequent insistence to return to pragmatic intuitions. He seems to have been caught by the novelty and missed the point: skepticism challenges precisely those intuitions he’s keen to retreat to! How is he certain, for example, that pragmatism is a ‘good’ we should all pursue, or one that is ‘useful’? What does it mean to be ‘useful’ or ‘good,’ anyhow? Useful for whom and to what end? And how did he come to those conclusions in the first place? He thinks that by digging his heels in he has escaped the skeptical onslaught, when in fact he has only provided better fodder!
Perhaps we should step back before getting ahead of ourselves: what even is skepticism as a philosophical position? The typical assumption is that it is the disposition to question everything, or to suspiciously consider arguments and evidence, an assumption my prose seemingly affirms. Of course, we could ask whether the skeptic is skeptical of their skepticism, and so perhaps it’s a worthless endeavor from the start. Moreover, in the 21stcentury, we often hear of skepticism or encounter a soi-disant skeptic, but we rarely think of it as a philosophical system unto itself, let alone an actual way of life deserving of adherence, something that sounds all too ironic. The contemporary skeptic is little more than an illiterate dogmatist consisting of a pitiful concoction of materialism, relativism and scientism. It would seem that skepticism is either self-refuting, misguided, or even dangerous, and if modernity (think Descartes) or post-modernity (think Derrida) are any indication, skepticism has only hindered the project of rational inquiry, not aided it. Therefore, it should be dismissed, refuted, or ignored entirely, right? That may be too rash. Skepticism has a rather long pedigree that does not begin in modernity, and certainly is not related to any of the garden-variety aberrations we find in contemporary life. It deserves more careful consideration, even if dream-scenarios and brains-in-vats give us a headache.
Enter Augustine of Hippo, who famously had a varied journey to the Christian faith, which, though often forgotten, included a period of explicit skepticism. As he recounts in Confessions Book V,
Accordingly, after the manner of the Academics, as popularly understood, I doubted everything, and in the fluctuating state of total suspense of judgment I decided I must leave the Manichees, thinking at that period of my skepticism that I should not remain a member of a sect to which I was now preferring certain philosophers. (Conf. V.25)1
It is Skepticism, not Platonism or Christianity, that Augustine identifies as the vehicle by which he cast off the dualist materialism of the Manichees. His flirtation with Cicero begins with the now lost work Hortensius, which enflamed his soul for philo-sophia and eventually gave way to sustained feasting on Cicero’s Academica (On Academic Skepticism) where Cicero lays out the Stoic-Skeptic debate about whether the truth can be found. It is no surprise that this rendezvous with skepticism—barely noted in the Confessions, but noted nonetheless—would lead Augustine to write his own treatise on the matter, Contra Academicos (Against the Academic Skeptics). In fact, it is the first extant work of his that we have. For those who see Augustine as the great church father responsible for refuting the heresies of Manicheanism, Donatism and Pelagianism, the work reads like a nifty handbook for dealing with skeptics and their bothersome attacks, so if you are predisposed to see Augustine as a Christian dogmatist, then it’s easy to miss his own skepticism, its importance, or that it is anything more than a minor episode in his intellectual and spiritual development. But are the only options outright skepticism or dogmatism? Did Augustine think skeptics brought something worthwhile to the intellectual table? Earlier in Book V he elaborates,
The thought had come into my mind that the philosophers whom they call the Academics were shrewder than others. They taught that everything is a matter of doubt, and that an understanding of the truth lies beyond human capacity. For to me that seemed clearly to be their view, and so they are popularly held to think. I did not yet understand their intention. (Conf. V.19)
There are two main points here: first, that the skeptics taught radical doubt and second, that the truth lies beyond our capacity. Additionally, per the previous quote, Augustine indicates that these two lead to a total suspense of judgment. But the real question is why did the Skeptics advocate radical doubt? Is not the assertion that the truth is beyond our capacities a dogmatic statement unto itself? Is it even possible to totally suspend judgment?
The debate between the Stoics and the Skeptics hinges on the Stoic definition of knowledge given by Zeno and centers on what is called a kataleptic impression, where ‘kataleptic’ means that which is apprehensible or graspable in such a self-warranting way that it could not be otherwise. If we want to be wise, therefore, we must restrict ourselves to such kataleptic impressions, as assent to impressions that fail to constitute knowledge would be irrational. Zeno’s definition of a kataleptic impression can be summed up as the following:
An impression, X, is kataleptic if
[a] X comes from what is (i.e. is true)
[b] X is impressed in accordance with what is (i.e. richness of detail)
[c] X could not be impressed from what is not (i.e. richness of detail is not imitable).2
As Charles Brittain explains,
Academic criticism of Stoic epistemology is centred, unsurprisingly, on Zeno’s definition of apprehension. The Academics argued that if this definition was correct, nothing could be apprehended, and hence, since all knowledge depends on apprehensions, nothing could be known at all. Their basic tactic, from the time of Arcesilaus onwards, was to grant that conditions [a] and [b] were often met, as Zeno claimed, but to argue that condition [c] was never obtained.3
The way the Skeptic would refute [c] would be to follow lines of inquiry similar to the ones taken at the start of this article, that is, by appealing to abnormal states of mind such as dreams or illusions, as well as pointing to indiscernible objects of experience, such as twins or eggs.4 Logically, the Skeptical reply goes thus:
 Some impressions are true [Stoic claim]
 If an impression, Y, is false, then Y is not kataleptic [Zeno’s definition (a)]
 If the content of a true impression, X, is not discernable from a false impression, Y, then X is not kataleptic [Zenos’s definition (c)]
 There is no impression that meets (c) [e.g. arguments from dreams, etc.]
 Thus there are not kataleptic impressions
 It is irrational to assent to non-kataleptic impressions [Stoic view]
 Therefore, it is irrational to assent to any impression at all.5
And here we discover what grounds radical doubt; if the truth depends on self-warranting apprehensions that could not be otherwise, and there is no apprehension that meets that criteria, then the truth cannot be found, and if the truth cannot be found—and we are likewise committed to the principle that only the wise man is happy such that to be wise means not falling into falsehood, a commonplace assumption in philosophy at the time—then it is perfectly rational to withhold assent; actually, it may be the only way to be rational. In short, we should doubt everything. The Stoics, however, level a serious counter-reply known as the “inactivity argument”:
 action requires assent to a certain kind of impression (e.g. beliefs)
 thus it is irrational ever to act
 (9) is absurd, therefore (7) is false.6
Even the most basic activity requires some kind of assent. If I outstretch my hand to pick up the coffee cup in front of me, then my doing so is predicated upon my believing that there is in fact a coffee cup in front of me, or, at the very least, having the impression ‘coffee cup,’ assenting to that impression, and acting on it. If the Skeptic is serious about (7), then the Skeptic cannot even pick up a coffee cup, and that would apply to all possible activities the Skeptic might undertake. Since the Skeptic clearly acts—they are having a conversation, for example—then that conclusion is absurd. QED, (7) is false. Either there are impressions we can assent to, or we are wholly irrational and should give up any hopes to the contrary.
It is at this point that you get three different flavors of Skepticism: Radical, Mitigated, and Fallibilism. The Radical Skeptic can tweak (8) by denying that one has to affirm the truth of impressions to act on them. One could, after all, merely approve of an impression as plausible to act on it, without any corresponding commitment to the impression being a true one. Likewise, the Radical Skeptic is by no means committed to Zeno’s definition, which would constitute dogmatic assent, but only adopts the definition for dialectical purposes. The Mitigated Skeptic could tweak (6) and argue that it is only sometimes irrational to assent to non-kataleptic impressions, but otherwise opinions are satisfactory for activity. Like the Radical Skeptic, they affirm one’s ability to act on plausible impressions, but, unlike the Radical, these plausible impressions can actually serve as rational justification for one’s activity, instead of merely the impetus for said activity; also unlike the Radical, the Mitigated Skeptic is so because they first assented to Zeno’s definition as a true one, and then commit to the conclusions that follow from it. Finally, Fallibilism could reject (c) of Zeno’s definition and instead argue that fallible knowledge is possible.7 At this juncture we could ask whether Fallibilism should still be considered Skepticism or something akin to epistemological modesty, a potentially attractive view in its own right, but I will leave that to the reflection of the reader.
So what kind of Skepticism did Augustine have in mind in the Confessions? Augustine tells us that the Skeptics asserted radical doubt, that the truth cannot be found, and that we should totally suspend judgment. When reframed in the logical order provided by Cicero, we see that by considering claims to knowledge, e.g. Zeno, they do not stand up to criticism, and so it seems the truth cannot be, or at least is not currently, found. Given the philosophical commitment to wisdom and the good life, that means we should go on radically doubting until we find some position that meets the condition for knowledge, which entails suspension of judgment until then. However, in light of the argument from inactivity, this suspension of judgment can be practically maintained through assent to plausible impressions. Given that Augustine says the above is what the Academics taught, he seems to have in mind Mitigated Skepticism, and it is this Mitigated Skepticism that convinced him to abandon Manicheanism.
But if we read those passages carefully, Augustine has a number of noteworthy qualifications. In both passages he mentions the “popular” understanding of the Skeptics, which, if what I said above is correct, he connects with the Mitigated view and is the one he took up in his youth. He also adds something about their “intentions” that he was yet to understand. Augustine was a Skeptic at some point in his life, of that we have no doubt, but his reflection on that Skepticism in the Confessions indicates that later in life he came to identify that Skepticism as only a popular, exoteric version, one that concealed some hidden intention, something esoteric, that he clearly came to understand later in life. But what is that esoteric dimension?
To be continued…
 Augustine Confessions, trans. Henry Chadwick, Oxford World Classics, 1991
 Cicero On Academic Skepticism, trans. Charles Brittain, Hackett Publishing Company, 2006, p. xx. For the definition of a katalaptic impression, see Acad. 1.40-42; for Cicero’s presentation of the Academic arguments see Acad. 2.40-42, 66-67, 78, 83. I’m following Brittain’s introduction rather closely, but also making necessary changes or additions to his formulations as I see fit for ease of understanding.
 Ibid. xxi
 Acad. 2.47-58, 84-89
 Ibid. xxii-xxiii
 Ibid. xxiii-xxxi
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Alexander Earl currently teaches Theology and History at a college-preparatory school in Santa Monica, California. He holds a Masters of Arts in Religion and Philosophical Theology from Yale Divinity School.