HISTORY OF SKEPTICISM. IN SEARCH OF CONSISTENCY
This book is an attempt to recreate the history of a current of thought that, for centuries, was called skepticism. It is also an attempt to present the current state of research on skepticism, focusing on the most recent interpretations of the works of ancient skeptics and contemporary positions in debates over skepticism. This book belongs to two disciplines of philosophy: the history of philosophy and epistemology. In pursuing both these lines, a historical reconstruction of the most important skeptical stances, ranging from ancient times to contemporary times, is connected with their assessment, particularly in terms of their consistency.
The skeptical stance is most easily expressed by the thesis “knowledge does not exist.” This particular thesis of global skepticism played an extremely significant role within the history of philosophy, but is also the position most likely to be attacked for a lack of internal consistency. If knowledge does not exist, how can we know, or prove this fact? Skeptics, who were not willing to keep quiet and stood by their skeptical view, were forced to search for answers to this accusation. Ancients differentiated between theory and practice, that is, between theory and situations where one could be guided by probability (Carneades), and/or phenomena (Sextus Empiricus). Modern thinkers pointed to other ways of learning about the world, ways outside of intellectual investigation, such as faith (William Ockham, Michel de Montaigne) or instinct (David Hume). That was their way of searching for a possibility to continue their skeptical discourse alongside everyday life and despite the conviction of knowledge’s nonexistence. However, solutions turned out to be ineffective and accusations kept reappearing. When following the history of skepticism, one can observe that a lack of consistency seems to be its inseparable feature (Burnyeat, 1976: 65) and that a willingness to escape the aforementioned accusation was a driving force behind the creation of its later incarnations. Peter Unger, a twentieth century skeptic, is not afraid of this lack of consistency (Unger, 1975: 6). In his opinion, this lack does not prove the falsity of skepticism. It merely reveals problems buried within human language and the thinking process.
Closer analysis of the inconsistency imbedded in skeptical stands shows that it is not only simple lack in logical consistency, or contradictions between different theses. It is rather a pragmatic inconsistency, the conflict between a proclaimed thesis and the assumptions hidden in its assertion as the act of speech. This theory will be the primary outcome of this work. On the basis of the analysis of actual skeptical stands, particularly those of Sextus Empiricus and David Hume, as well the use of tools taken from contemporary epistemology (particularly the language-game theory of Wittgenstein and speech act theory of Searle), it is clear that pragmatic inconsistency is the best way of conceptualizing inconsistencies embedded in skepticism.
The reconstruction of the history of skepticism, with small exceptions concerning Pyrrho of Elis, will be limited to the culture of the West and focused on philosophical skepticism (religious skepticism and other varieties will appear from time to time as well). Between the many different forms of philosophical skepticism, my attention will primarily be focused on global skepticism, since this is the form that is most exposed to accusations of a lack of consistency. Other important participants in the debate (e.g. Descartes), who either deepened the argumentation of skepticism, or formulated an anti-skeptical strategy, will be the object of the reconstruction alongside well-known or declared skeptics.
The following chapters, except for the first one focused on defining with precision the meaning of the term skepticism, will be devoted to the consecutive stages and epochs in the history of skepticism: ancient, medieval, modern and contemporary. The main skeptical strands of every epoch will be presented and the most important ones will undergo more meticulous analysis, with particular focus on their consistency. Concerning antiquity, Sextus Empiricus will be presented as the main representative of skepticism, principally due to the survival of his works. The Middle Ages will be represented by William Ockham, as a typical, Christian skeptic-fideist. When talking about modernity, we will turn to David Hume as a representative of the most radical and influential variety of skepticism and finally, in the context of the contemporary world, Peter Unger will be presented as the most famous self-declared, contemporary skeptic, in addition to Kripke-Wittgenstein, due to their new form of skepticism of meaning.
The book makes many references to Izydora Dąmbska (1904-1983) and Richard Popkin (1923-2005). Izydora Dąmbska wrote a lot about ancient and modern skepticism and made some assertions about medieval and contemporary skepticism. Her research was my starting point and guide in the reconstruction of the history of skepticism. Richard Popkin wrote The History of Scepticism. From Savonarola to Bayle (2003). The book covers the history of modern skepticism. I continue this work extending the reconstruction of skepticism from ancient times to contemporary times, from Pyrrho to Kripke and beyond.
THE NOTION AND TYPES OF SKEPTICISM
Not simply skeptical stances, but the very term “skepticism” has undergone considerable evolution. Nevertheless, it would be hard to conduct the aforementioned reconstruction without using skepticism as understood in a contemporary manner. As already indicated, I will assume that the word skepticism stands for a thesis claiming that knowledge does not exist. I will treat this contemporary thesis as a model of skepticism in comparison with less typical theses or those positions that do not propose any thesis whatsoever.
Genealogy of the Term Skepticism
Skepticism was not always named this way and the representatives of such schools were not always called skeptics. Along with their critics, the skeptics of previous ages did not use the term skeptikoi (σκεπτικοί, skeptics) to name thinkers from the schools of skepticism, even though the Greek verb skeptomai, the noun skepsis and the adjective skeptikos already existed. The verb skeptomai, meaning “I look,” “I research” can be spotted already in the works of Homer. Many writers, including Thucydides, Hippocrates, Sophocles, Plato (Lach. 185b) and Aristotle (EN 1103b), use the verb regularly. The noun skepsis, meaning “a look,” “research” can be found in the works of Plato (Phaed. 83a, Thaet. 201a) and Aristotle (Phys. 228, EN 1159b). All of this usage comes from the pre-skeptic period. However, in the times of Pyrrho and the academic skeptics, the situation was similar. Pyrrho’s student, Timon of Phlius, uses the word skeptosyne in his poem Silloi, but it carries its common, vernacular meaning “research” (Bett 2010d: 5). The adjective skeptikos used at that time did not refer to the representatives of the skeptical school of thought, but meant “curious” or “inquiring.” This is the case with the Epicurean Philodemus (Rhet. 1.191) from the 1st century B.C., Plutarch (Moralia 990A) and sometimes Philo of Alexandria from the 1st century A.D. (De Ebrietate 202). In works by Philo of Alexandria, skeptikos is used for the first time, as far as we know, as the name for neo-pyrrhonists (Congr. 52, por. Bett 2003: 148). In the 2nd century, the adjectival noun skeptikoi, referring to the school of philosophical thought, appears in many different sources: works by the sophist Lucian of Samosata (Vit. Auct. 27.40), the Roman writer Aulus Gellius (NA 11.5) and a little later in the writings of Sextus Empiricus (PH 1.3-21). In the 3rd century, in the works of Diogenes Laertius (DL 9.70), it is already a well-established, technical term. Sextus will also use the noun skepsis as name for the branch of philosophy (PH 1.5,7).
The word skeptikoi, or its Latin equivalent, are nowhere to be found in the oldest preserved, direct sources on the Greek skeptics, which are the works of Cicero from the 1st century B.C. He did not write about “skeptics” but about “academics” who, for him, were the supporters of epochē, or the suspension of all judgement. Plutarch called academics “men, who suspend their judgement of everything” (Adversus Colotem 1121E=LS 68H1). Epochē was, for Cicero, a fundamental characteristic of academic skepticism. He mentioned Pyrrho as a moralist, famous for his indifference, but not a supporter of epochē (contrary to what Aristocles, Sextus Empiricus or Diogenes Laertius later wrote about him). The absence of the word epochē in the works of Pyrrho could be a possible excuse for Cicero (however, sources reveal the presence of a similar word - aphasia - which means “not making judgements”). Regardless of the right answer to this mystery, neither the writings of Pyrrho or Cicero use the term skeptikoi as a name for a philosophical school. We can presume that the term was coined in the neo-pyrrhonian school of Aenesidemus and Philo of Alexandria, who has conveyed the findings of Aenesidemus to us and provided the very first example of such usage.
At the beginning of the 2nd century, the word skeptikoi was clearly used to designate Pyrrho’s followers, as well as academics. It might have played the role of a unifier for these two skeptical currents of thought. This was the goal of Favorinus, a student of Plutarch (according to Filostratos I.8.6; 2008: 32). He was an admirer of Pyrrho and combined academic skepticism with neo-pyrrhonism. Aulus Gellius, a citizen of Rome, was Favorinus’ student. Composed in Latin, his writings from the 2nd century include the Greek word skeptikoi as name of the school. In Noctes Atticae, Aulius Gellius questions the difference between the academics and pyrrhonists (he refers to this question as an old problem, debated by many Greek authors) and, collectively, calls them skeptikoi (skeptics - those who look and examine, but do not find a solution). He mentions other names as well: ephektikoi (ephectics - those who suspend judgement) and aporetikoi (aphorectics - those who are helpless when confronted with a problem)1. Sextus Empiricus and Diogenes Laertius will likewise write about this later on. Sextus will add a specific name to the three mentioned before - pyrrhonists (PH 1.7) - and Diogenes (DL 9.70) will contribute with his zetetikoi (zetetics - those who search, but never find). The first and the last names are hard to distinguish, but we can assume that the first refers to a lack of understanding, despite analyzing and drawing conclusions, while the last one refers to the lack of an answer, despite searching and inquiring. These four names, with the exception of the one specific name (pyrrhonists), grasp the important features of the skeptical attitude: a lack of results after search and examination, and a suspension of all judgement and observing problems without solution. All these names were used during the first centuries of our era (Floridi 2002: 104-5). The name ephectics, used by Clement of Alexandria (Strom. 8.8.15) and neo-platonists from the 6th century (Ammonius, Simplicius, Olympiodoros; compare Floridi 2002: 20) had a decent range, but “pyrrhonists” and “skeptics” ultimately dominated the others. One should add that during the Middle Ages, under the influence of St. Augustine and Cicero, “skeptics” were called “academics.”
In the time of the neo-pyrrhonian school’s activity (Aenesidemus, Agrippa, Sextus Empiricus), under the patronage of Pyrrho, its representatives were called “pyrrhonists” (compare Photius’ Bibliotheca, 169b). However, the word “skeptic” was increasingly popular over time (Floridi 2002: 103). It seems that the main role in this process of establishing terminology was played by Sextus Empiricus, who wrote about skeptics and skepticism (PH 1.1-30) and whose works became the main source of information on skepticism for modern Europe. On the one hand, Sextus was not friendly toward academics (and especially towards Carneades), depriving them of the right to call themselves “skeptics” (instead calling them “negative dogmatics”). On the other hand, he assumed a certain distance when writing about Pyrrho, who was known as the originator of skepticism, but whose exact ideas were not that well known to Sextus (PH 1.7). Most likely written in accordance with the tradition of the neo-pyrrhonian school, his Outlines of Pyrrhonism hardly ever names the representatives of that school “pyrrhonists” (PH 1.7,11,13) and more often calls them “skeptics” (skeptikoi). Also, in the Lives and Opinions of Diogenes, it is a term used more often than “pyrrhonists” (DL 9.11). Diogenes writes about the problems resulting from the usage of the term “pyrrhonism” as caused by the lack of a doctrine in the teachings of Pyrrho (one can become a pyrrhonist only through mimicking Pyrrho’s style of life). At the beginning of Outlines, Sextus divides philosophers between dogmatics, who claim that they have found the truth (e.g. Aristotle), academics, who claim that the truth is impossible to attain (e.g. Carneades) and skeptics, who still search for the truth (PH 1.1-4). This famous division of philosophical stands, cited by Montaigne and repeated by his followers, confirms the key role of the term “skepticism” in the history of doubting philosophers. The broad definition of skepticism from the beginning of Sextus’ Outlines is defined more precisely later in the work with the introduction of the rule of the suspension of judgement.
The choice made by Sextus likewise became the choice of modern philosophy. In the 9th century, Photius also assumed that pyrrhonists are some kind of skeptics (Bibliotheca 169b). In 1430, when Traversari’s Latin translation of Diogenes’ Lives and Opinions appeared and began to circulate, the Latin word scepticus entered the dictionary of modernity (Popkin 2003: 17, Hankinson 1995: 10, Floridi 2002: 14). In medieval Latin, the word scepticus did not exist. It was transliterated from the Greek skeptikos as a technical term, and so the literal translation - “researcher or explorer” - could be misleading. The Latin term scepticus appeared in the 2nd century in Attic Nights by Aulus Gellius and, similarly to the terms we find in the works of Cicero, it could have been a template for Renaissance translators. In 1562, the printed Latin translation of Sextus’ Outlines of Pyrrhonism by Stephanus appeared. Only then did the word scepticus become truly popular in Latin Europe (Popkin 2003: 18, Hankinson 1995: 11, Floridi 2010: 281). The publication of Montaigne’s Essays (1580) introduced the French term sceptique and further popularized the notion of skepticism.
Thanks to the title of Sextus Empiricus’ work, Outlines of Pyrrhonism, and a chapter devoted to Pyrrho in Diogenes Laertios’ Lives, the term pyrrhonism did not disappear. It was moderately popular in the modern epoch and used by Montaigne in his Essays and by Hume in his Treatise and An Enquiry. At present, it operates in the background and is used by specialists researching different varieties of ancient skepticism (“pyrrhonism” is a current of thought ascribed to Pyrrho, Aenesidemus, Agrippa and Sextus Empiricus, while “academic skepticism” is connected to Arcesialus, Carneades and other members of the Academia). The word “skepticism,” in its different linguistic variations, became a term that denoted both academicism and pyrrhonism, alongside other positions questioning the existence of human knowledge.
Evolution of the Idea of Skepticism.
2.1. Ancient skepticism as a suspension of judgements aspiring to be the truth.
We differentiate between two types of skepticism in ancient times: pyrrhonism and academic skepticism. The first was radical, while the second was moderate. In both cases, the skeptical attitude involved epochē - a suspension of judgement. Epochē is not a theoretical posture, but an attitude toward life that is recommended in order to avoid suffering and achieve happiness. It entailed life without making judgements of any kind or a life without any beliefs.
Sextus Empiricus passed on the radical version of skepticism. The arguments which he presents in his works suggest that there is no way to rationally prefer any given judgement, prior to its negation. Observational phenomena are dependent on circumstances and every attempt to justify any given thesis leads to infinite regress or results in a vicious circle. For the same reason, it is impossible to establish a criterion of truth, or present a valid proof. Since no belief can be guaranteed as true, pyrrhonians simply recommended a life without belief. Sextus states that such life is possible and explains that it consists of the passive acceptance of sensations and following customs and stereotypes imbedded in us by society.
Academic skepticism was decidedly more moderate. In this context, epochē is concerned with theory and not practice. There are no criteria for truth and all judgements are doubtful, but there still exists a need to be guided in one’s everyday actions. Guidance through persuasive phenomena seems sufficient. Carneades suspends all judgement, but in practice he approves of what is subjectively probable (pithanon). Academics, while attempting to solve the conflict between skepticism’s assumptions and requirements of everyday life, discovered the so-called, weak assertion (approval of what is not certain but probable or persuasive). Pyrrhonists, or at least Sextus and Aenesidemus, considered the approval of uncertain phenomena to be a betrayal of skepticism.
This moderate version of skepticism was passed on to modernity by Cicero and St. Augustine and it was this version that has formed the modern understanding of skepticism as a lack of certainty. Even the discovery of Sextus’ works during the Renaissance did not change that perception. His arguments against the reliability of our senses and the impossibility of rational justification have been labeled as arguments against established knowledge.
2.2. Medieval skepticism: the weakness of human judgements contrasted with God’s omnipotence.
Christian thinkers assumed that the skepticism of Pyrrho was a completely absurd position (the assent that nothing can be assented to) and not in accordance with the truth of revelation. None of the medieval thinkers declared themselves to be radical skeptics. From time to time, there were instances of acceptance displayed toward the moderate, academic skepticism, as understandably combined with the belief that faith is the only source of truth (John of Salisbury). Over time, a Christian version of skepticism emerged, concerning itself with God’s omnipotence. This allowed for the possibility of the human mind to be tricked or cheated into false conviction. The confrontation of human cognitive abilities with the idealized mind of God created a gap between objective truth and man’s convictions, sometimes leading to cognitive pessimism. On the other hand, the Creator was a warrant for the very concrete possibility of knowing the world, which saved medieval philosophy from radical skepticism.
Medieval skepticism was focused on the weak cognitive abilities of man, assessed without God’s help and in a situation where divine intervention took place in the form of misleading man. It doubted whether the human mind could reach knowledge on its own and without any assistance. Already in the Middle Ages, one can find the emergence of idea of probable knowledge in works of Nicholas of Autrecourt and Jean Buridan. The skeptic Nicholas of Autrecourt claimed that there is no certain knowledge, although he admitted that there is probable knowledge. His adversary, the anti-skeptic Jean Buridan was of the opinion that there is still probable knowledge, even without certainty, and that this establishes the very existence of knowledge. For Nicholas, skepticism was constituted by a lack of certain knowledge and the lack of any knowledge for Buridan.
Medieval skeptics were also local skeptics (see later distinctions between types of skepticism) and fideists. William Ockham assumed that we lack certain knowledge based in reason about God (but we know the truth about God through faith). He thought that if there is no divine intervention, according to the natural order, we are equipped with knowledge about the world that is certain. Nicholas of Autrecourt broadened skepticism, claiming that we do not posses certain knowledge about the existence of observed objects or causal relations. Nevertheless, he accepted the certainty of a priori knowledge that can be reduced to the law of non-contradiction.
2.3 Modern skepticism: doubting the value of judgements aspiring to be knowledge
Ancient skepticism combined with Christian fideism was reborn in modernity. Excluding Montaigne, skepticism was no longer treated as practical wisdom. However, the theoretical importance of skepticism was duly noted. When discussing issues from the realm of skeptical thought, the idea of knowledge that required certainty was strongly emphasized (it should be noted that Francis Bacon was developing the idea of probable knowledge at the same time). Modern skepticism, in contrast with its ancient counterpart, did not pose any threat to common beliefs, which were excluded from the reach of skeptical doubt as belonging to a practical, rather than theoretical, order. In the theoretical order, certain knowledge was pursued and skepticism took the form of doubt in the value of judgements which aspired to be exactly that - certain knowledge.
In particular, Montaigne’s skepticism is a thesis about the lack of certainty, which was stated with as much uncertainty as was the case in other formulations. “The philosophy of pyrrhonists is to shake, wobble, doubt and seek - not to strengthen your beliefs in nothing” (E 12). Rene Descartes, in his stage of methodical skepticism, wrote: “there is nothing of all those things I once thought true, of which it is not legitimate to doubt” (Med. 1. 21). David Hume, in one of the more desperate moments of his skepticism, simply stated that “all is uncertain” (THN, I.IV). Hence, what specifically marked modern skepticism was doubt and a lack of certainty. Instead of doubting already established judgements, the ancients preferred to restrain themselves from passing new judgements. They suspended their judgements due to the equipollence (isostheneia) between contradictory theses. Modern thinkers doubted and backed their stands with the Cartesian hypothesis and logical possibility of error. In his commentary to Sextus, Leibniz observes that two judgements are never ideally isosthenic and usually one of the sides dominates (Popkin 2003: 269).
Although modern skepticism turned out to be far more understanding of man’s psychology than its ancient predecessor, it managed to break the natural bond between human cognitive abilities and nature. The idealism of Descartes and his hypothesis allowed for such radical doubt that it placed the very existence of the world in question.
Popkin rightly observed that during the Enlightenment, the main function of skepticism was in opposition to religion. Religious skeptics of the Renaissance were replaced by non-religious skeptics in the Englightenment (Popkin 1988: 145). In the times of Pierre Bayle, George Berkeley and David Hume, while not synonymous, skepticism very nearly implied atheism (Popkin 2003: 246). This transformed meaning remains alive, especially outside of philosophical discourse, as a common definition for the word “skepticism.” In typical philosophical and especially epistemological debates over human knowledge, the understanding of skepticism remained religiously neutral, similarly to the usage of Descartes.
2.4 Contemporary skepticism: paradoxical thesis on the non-existence of knowledge and meaning.
At present, modern doubt seems to have gone missing. The manifestation of its end might be signaled by the common belief in the non-existence of certain knowledge. In short, the contemporary understanding of knowledge and rationality has been weakened and no condition of certainty has since reemerged. By contrast, the idea of probable knowledge is now widespread and well established. As a result, the need to distinguish between fallibilism and skepticism emerged. The stance of Charles S. Pierce and William James - the lack of certain knowledge (fallibilism) and the existence of some kind of knowledge (anti-skepticism) - has generally been accepted. Arguments that were sufficient for Hume to take a skeptical stand (knowledge does not exist), are, after a weakening of the conditions for establishing what is knowledge, presently sufficient only for fallibilism (knowledge is uncertain). In other words, fallibilism is a belief that knowledge exists, although it is uncertain. Skepticism, by contrast, is a belief that knowledge does not exist at all. Between fallibilism and skepticism we can observe a change in our understanding of what knowledge actually is.
Within contemporary philosophy, skepticism - as a philosophical stance - which we are supposed to either accept or debate, is expressed in the form of an abstract thesis. After all, it is hard to debate statements about a “lack of judgement,” or “attitude of doubt.” And as it turns out, doubt expressed in the form of a thesis is itself paradoxical. The thesis claims that no knowledge exists, not even uncertain knowledge, and that somewhere there is a rational justification to be found. These thesis cannot be rationally held without creating a contradiction. It is therefore no surprise that they are rarely accepted, but often debated (similarly to relativism and determinism). They function within philosophy as a kind of paradox which one must tackle. Peter Unger declared himself to be a skeptic and defended his claim by saying that “no one ever knows anything about anything” and “no one ever has a justified or rational conviction about anything” (Unger 1975: 1). However, he later abandoned skepticism for the sake of contextualism and philosophical relativism. He admitted that if knowledge requires certainty, then skepticism in the form of thesis about the non-existence of knowledge is unavoidable. But if knowledge does not require certainty, then skepticism becomes groundless. Philosophical solutions of the problem of skepticism were, to his mind, relative to the meaning of the word “knowledge.”
The contemporary model of skepticism uses the concept of strong knowledge when addressing the question of knowledge itself, thereby foregoing its own epoch that accepted the concept of weak knowledge. The weakening of the concept of knowledge resulted in the absorbing of common beliefs, which led to the return of their critique as a part of contemporary skepticism (people are not deprived of the right to have their own beliefs, as in ancient times, but the status of these beliefs as knowledge is questioned).
Subtle deliberations over the language and mind recently lead to the emergence of the skepticism of meaning (the meanings of our words do not exist, Kripke-Wittgenstein) and skepticism of the content of self-consciousness (we do not know the content of our own consciousness, according to Daniel Dennett). This results in a further deepening of skepticism regarding the question of the possibility of knowledge. The contemporary skeptical hypothesis sketches the possibility that all our beliefs are false, the meanings of our words are unclear, and the entirety of self-consciousness is illusory. We are left turning back to everyday life, without understanding it and abandoning any theorizing of it. Today’s skepticism is often a skepticism of the second order, pondering over the possibility of building a theory of knowledge.
In summary, ancient skepticism was a philosophy of not passing any judgements (epochē) on the outside world, and it was likewise an attempt to live without any convictions. Medieval skepticism was a recognition of the weaknesses of human cognition against the omnipotence of God. Modern skepticism is a philosophy of doubting human judgements which aspire to be knowledge. Contemporary skepticism is an abstract and paradoxical thesis about a lack of any knowledge or justification, and an unclearness of meaning resulting from the illusory character of the content of self-consciousness.
In the end, all these forms of skepticism are based on a lack of certainty, or fear that we do not posses knowledge that would fulfill the condition of being true (there is no warranty of truth). The fundamental divide resides between ancient and modern skepticism, which is between the ancient suspension of judgment and modern doubt about the value of judgements. Modern thinkers dismissed the suspension of judgments, arguing instead that beliefs can not be managed. They have recognized the existence of common beliefs and limited themselves to assessing their value. In other words, they have distinguished psychology (the description of mechanisms of acquiring and controlling beliefs) from epistemology (the assessment of the cognitive value of beliefs).
Working from ancient psychology, we might conclude that ancient arguments are those stemming from uncertainty. They point to the possibility that knowledge exists. The concept of knowledge has changed over time, but skeptics kept approaching it seriously, treating it as a manifestation of a willingness to reach objectivity and truth. A lack of certainty raised their suspicions as to whether we possess any knowledge at all. And so, the entire history of development of the global skepticism could be contained in our aforementioned thesis: “Knowledge does not exist.”
Types of Skepticism and Related Terminology
When comparing popular and philosophical skepticism, Peter Klein states that the popular variety is about a doubting attitude for which we can eliminate reasons, while the philosophical strand does not allow for any answers. For example, if we doubt whether a bird sitting on a branch is a sparrow, there is a way to alleviate the doubt by referring to pictures and descriptions of sparrows (shape, size, color, and behavior). Common doubts are usually local and appear in the context of knowledge we do not doubt. Klein is thinking in line with John Austin, who states, in his Other Minds, that we answer typical questions (e.g. Is this a bumblebee or a goldfinch?) by providing justifications, and we can know in advance what the possible answers might be (identification, description). The skeptic, on the other hand, poses questions that we do not know how to answer (e.g. Is this table real?), because there is no readymade template of an answer (Austin 1993: 119). But if I do not know if that is a table (an object well known to you or me), I do not know anything. Philosophical doubts are global and that is why there is no practical solution at hand (Klein 2010: 2-3). If a skeptic doubts if we can ever know anything, or even have a justified conviction - it is not enough to be more vigilant and commit more time to the uncertain cause in order to resolve pertaining doubts (Williams 1999: 37).
Aside from popular and philosophical skepticism, there are also varieties of religious and political skepticism that can be observed. The religious skeptic is a disbeliever, an atheist almost, unwilling to rely on revelation. Izydora Dąmbska and Richard Popkin stated that “the most common usage of the term skeptic is in relation to a religious disbeliever” (Popkin 2003: 246, compare Dąmbska 1948b: 79). The epistemological sense of skepticism that I am describing in this book is secondary in our culture. The first and most immediate association with the word “skeptic” is “man having an issue with religion.” The political skeptic, on the other hand, is a person who doubts the chances for successfully realizing a political plan. For example, the euro-skeptic does not believe that the idea of joining European nations into one political body will be advantageous to all of members. These kinds of skepticism are, as with practical attitudes, based on concrete rationale and close to popular skepticism, but they are also close to philosophical skepticism in that they are concerned with truly difficult problems.
According to Izydora Dąmbska and Michael Williams, we are supposed to distinguish between theoretical, practical and normative layers within philosophical skepticism (Dąmbska 1948a: 80, Williams 2010: 291). It is a theoretical thesis - the non-existence of knowledge - a practical attitude of doubting and resignation from any pretense to knowledge, forsaking any convictions (in ancient terms, suspending judgement), and a norm calling to “refrain from judgement!” The rational and practical strands of skepticism are based on theoretical skepticism and are a realization of normative skepticism. The theoretical layer dominates contemporary skepticism, but practical and normative layers dominated its ancient predecessor.
When presenting historical positions, I will distinguish, according to the strength of assertion, between radical and moderate skepticism. Radical skepticism in the ancient period was principally the philosophy of Sextus Empiricus, who refused even the weak assertion and recommended life without any convictions. In modernity, radical skepticism was a thesis about the non-existence of knowledge, assuming the strong assertion, which was merely a theoretical figure, debated widely but rejected by everyone. Moderate skepticism in antiquity is represented by the philosophy of Carneades, who allowed for the weak assertion and a limited the range for epochē. During modernity, it is the skepticism accepted by Hume in An Enquiry, in which the skeptical thesis is treated as equally uncertain as all other convictions. By implication, the critique of these convictions must be limited.
Philosophical skepticism in its consistent form should not be a thesis. That is why the ancients talked about the suspension of judgements and modern thinkers perceived doubting as an attitude rather than a thesis. In practice, these attitudes needed to be somehow described and justified. That is how skeptical arguments and the thesis with weakened assertion were created. At present, we know that practical attitudes hide theoretical assumptions and that any attempts to escape assertion are useless.
Skepticism as a thesis can also be divided into types according to the subject of skeptical critique. Ethical skepticism is a thesis claiming the non-existence of good and evil (Sinnot-Armstrong 2006). Skepticism concerned with religious beliefs will be a thesis about a lack of knowledge concerning the existence of God, his characteristics and/or goals (Schellenberg 2009). And finally, skepticism questioning the existence of the outside world (Greco 2008a) contradicts our knowledge of all external things, except phenomena, while skepticism toward other minds will contradict the claim of the existence of knowledge or conscious experiences of others.
The most philosophically sublime and most regularly debated form of contemporary skepticism is a global skepticism concerned with knowledge. As we have previously stated, it is the thesis which reads: “knowledge does not exist.” This particular form of skepticism is accused of incoherence, and it is this argument which is at the center of this book. The skepticism about knowledge can be divided into many different sub-categories. It can be concerned with the lack of knowledge or impossibility of knowledge - both local and global, and each of the four can be of the first or second order (“no one knows if s/he knows”. The thesis “knowledge does not exist” is global first order skepticism about the lack of knowledge. The rational justification of beliefs is the subject of similar skepticism in all of these varieties.
The novelty of contemporary skepticism is the skepticism of meaning and mental content (the content of self-consciousness). “It is impossible for any word to have any meaning” (Kripke 2007: 93), in the sense of existence of facts of meaning, which would constitute those meanings. This is the thesis of the skepticism of meaning. There is also skepticism that has emerged within the philosophy of mind. “What Descartes has seen as the most important - the direct, introspective grasp of the elements of consciousness - turns out to be not entirely true. It is a by-product of the way in which brain fulfills its quest of approaching” (Dennett 1994: 237). It could be formulated in the form of a thesis: “Mental contents and contents of self-consciousness are an illusion.”
The terms most closely related to skepticism are agnosticism and fallibilism. Agnosticism contradicted with the ancient skepticism understood as the lack of a thesis. It is a negative dogmatism in the form of thesis claiming inscrutability (for example: truth is inscrutable, the existence of God is inscrutable, the world is inscrutable). At the moment, when skepticism is interpreted as a thesis about the non-existence of knowledge, the difference between the two currents of thought may be blurred and might be limited to matters of aspect and degree. Agnosticism is perceived today as a synonym for skepticism, or its more radical version.
The rejection of certain knowledge is so common today that it no longer characterizes skeptics (almost every philosopher could end up being a skeptic). Skepticism is debated as a stance that could threaten all of knowledge, also in its popular variety. The very lack of certainty is not impressive. The difference between skepticism (saying that knowledge does not exist) and fallibilism (asserting that certain knowledge does not exist) is a topic of ongoing, lively debate.
Fallibilism has its pessimistic and optimistic side. The pessimistic one focuses on highlighting our inclination to commit mistakes and being mislead by our senses and mind. Sometimes we do not even realize we are being mislead and our scientific theories are incomplete and incorrect. At best, we posses knowledge that is fallible (fallible). On the optimistic side, this fallible knowledge is some knowledge after all. The fallibilist believes that it is true, although he admits that its falsity cannot be excluded (Harpner 2010: 339).
We ought to note that fallibilism is generally accepted, while skepticism lacks open or declared supporters. Hillary Putnam finds the skeptical hypothesis inconsistent, and yet he is a fallibilist (he holds no convictions that are guaranteed not to be revised in the future, Putnam 1994: 152). The difference between fallibilism and skepticism can seem purely emotional: skepticism being associated with cognitive desperation and fallibilism connected with cognitive hope (Hookway 2008: 312). Michael Williams formulated this difference nicely: skepticism is a total doubt, while fallibilism is a potential total doubt, but not in everything at once. The difference is not logical, but pragmatic (concerned with the procedure of doubting as a form of action). Williams points to a number of skeptical assumptions that are hard to accept (an inadequate concept of knowledge, asymmetrical requirements for justification) and is ultimately opposed to skepticism. However, he accepts fallibilism: we have knowledge but we cannot logically exclude the possibility of its falsity (Williams 2001: 41).
In conclusion, today’s skepticism (knowledge does not exist) is more than fallibilism (certain knowledge does not exist) - it is a negation of all knowledge, also the uncertain variant. Agnosticism (the world is inscrutable) has become a synonym of skepticism, or skepticism radicalized. Contemporary skepticism detached itself from fallibilism, but managed to attach itself to agnosticism.
It is worth mentioning the relation between skepticism and relativism. These two positions, in their most radical version, encounter the same problem with self-refutation, and the arguments supporting relativism are sometimes listed as arguments supporting skepticism (for example, the ten trails of Aenesidemus). However, these are separate positions. Unger (1984) rejected skepticism (knowledge does not exist) for the sake of relativism (an answer to the question of knowledge’s existence depends on the concept of knowledge we adopt). In summary, skepticism assumes the objective concept of truth and a strong concept of knowledge requiring certainty. It is a thesis about our terminology and language, both skeptical and anti-skeptical. Relativism is a thesis in meta-language and skepticism is usually a thesis formulated in objectival language (Amini, Caldwell 2011: 102). Common to both stances is the questioning of the value of human convictions.