by Tim Harding
Dictionaries often draw a distinction between the modern common meaning of skepticism, and its traditional philosophical meaning, which dates from antiquity. The usual common dictionary definition is ‘a sceptical attitude; doubt as to the truth of something’; whereas the philosophical definition is ‘the theory that some or all types of knowledge are impossible’. These definitions are of course quite different, and reflect the fact that the meanings of philosophical terms have drifted over the millennia. The contemporary meaning of ‘scientific skepticism’ is different again, which I shall talk about later.
I should say at the outset that whilst I have a foot in both the scientific and philosophical camps, and although I will be writing here mainly about the less familiar philosophical skepticism, I personally support scientific skepticism over philosophical skepticism, for reasons I shall later explain.
But why are these definitions of skepticism important? And why do we spell it with a ‘k’ instead of a ‘c’.? As an admin of a large online skeptics group (Skeptics in Australia), I am often asked such questions, so I have done a bit of investigating.
As to the first question, one of the main definitional issues I have faced is the difference between skepticism and what I call denialism. (The second question I shall answer later). Some skeptical newbies typically do a limited amount of googling, and what they often come up with is the common dictionary definition of skepticism, rather than the lesser known scientific skepticism definition that we Australian skeptics use. They tend to think that ‘scepticism’ (with a ‘c’) entails doubting or being skeptical of everything, including science, medicine, vaccination, biotechnology, moon landings, etc, etc. When we scientific skeptics express a contrary view, we are sometimes then accused of ‘not being real sceptics’. So I think definitions are important.
In my view, denialism is a person’s choice to deny certain particular facts. It is an essentially irrational belief where the person substitutes his or her personal opinion for established knowledge. Science denialism is the rejection of basic facts and concepts that are undisputed, well-supported parts of the scientific consensus on a subject, in favour of radical and controversial opinions of an unscientific nature. Most real skeptics accept the findings of peer-reviewed science published in reputable scientific journals, at least for the time being, unless and until it is corrected by the scientific community.
Denialism can then give rise to conspiracy theories, as a way of trying to explain the discrepancy between scientific facts and personal opinions. Here is the typical form of what I call the Scientific Conspiracy Fallacy:
Premise 1: I hold a certain belief.
Premise 2: The scientific evidence is inconsistent with my belief.
Conclusion: Therefore, the scientists are conspiring with the Big Bad Government/CIA/NASA/Big Pharma (choose whichever is convenient) to fake the evidence and undermine my belief.
It is a tall order to argue that the whole of science is genuinely mistaken. That is a debate that even the conspiracy theorists know they probably can’t win. So the most convenient explanation for the inconsistency is that scientists are engaged in a conspiracy to fake the evidence in specific cases.
Ancient Greek Skepticism
The word ‘skeptic’ originates from the early Greek skeptikos, meaning ‘inquiring, reflective’.
The Hellenistic period covers the period of Greek and Mediterranean history between the death of Alexander the Great in 323 BCE and the Roman victory over Greeks at the Battle of Corinth in 146 BCE. The beginning of this period also coincides with the death of the great philosopher, logician and scientist Aristotle of Stagira (384–322 BCE).
As he had no adult heir, Alexander’s empire was divided between the families of three of his generals. This resulted in political conflicts and civil wars, in which prominent philosophers and other intellectuals did not want to take sides, in the interests of self-preservation. So they retreated from public life into various cloistered schools of philosophy, the main ones being the Stoics, the Epicureans, the Cynics and the Skeptics.
As I mentioned earlier, the meanings of such philosophical terms have altered over 2000 years. These philosophical schools had different theories as to how to achieve eudaimonia, which roughly translates as the highest human good, or the fulfilment of human life. They thought that the key to eudaimonia was to live in accordance with Nature, but they had different views as to how to achieve this.
In a nutshell, the Stoics advocated the development of self-control and fortitude as a means of overcoming destructive emotions. The Epicureans regarded absence of pain or suffering as the source of happiness (not just hedonistic pleasure). The Cynics (which means ‘dog like’) rejected conventional desires for wealth, power, health, or fame, and lived a simple life free from possessions. Lastly, there were the Skeptics, whom I will now discuss in more detail.
During this Hellenistic period, there were actually two philosophical varieties of skepticism – the Academic Skeptics and the Pyrrhonist Skeptics.
In 266BCE, Arcesilaus became head of Platonic Academy. The Academic Skeptics did not doubt the existence of truth in itself, only our capacities for obtaining it. They went as far as thinking that knowledge is impossible – nothing can be known at all. A later head of the Academy, Carneades modified this rather extreme position into thinking that ideas or notions are never true, but only probable. He thought there are degrees of probability, hence degrees of belief, leading to degrees of justification for action. Academic Skepticism did not really catch on, and largely died out in the first century CE, with isolated attempts at revival from time to time.
The founder of Pyrrhonist Skepticism, Pyrrho of Elis (c.365-c.275BCE) was born in Elis on west side of the Peloponnesian Peninsula (near Olympia). Pyrrho travelled with Alexander the Great on his exploration of the East. He encountered the Magi in Persia and even went as far as the Gymnosophists in India, who were naked ascetic gurus – not exactly a good image for modern skepticism.
Pyrrho differed from the Academic Skeptics in thinking nothing can be known for certain. He thought that their position ‘nothing can be known at all’ was dogmatic and self-contradictory, because it itself is a claim of certainty. Pyrrho thought that the senses are easily fooled, and reason follows too easily our desires. Therefore we should withhold assent from non-evident propositions and remain in a state of perpetual inquiry about them. This means that we are not necessarily skeptical of ‘evident propositions’, and that at least some knowledge is possible. This position is closer to modern skepticism than Academic Skepticism. Indeed, Pyrrhonism became a synonym for skepticism in the 17th century CE; but we are not quite there yet.
Sextus Empiricus (c. 160 – c. 210 CE) was a Greco-Roman philosopher who promoted Pyrrhonian skepticism. It is thought that the word ‘empirical’ comes from his name; although the Greek word empeiria also means ‘experience’. Sextus Empiricus first questioned the validity of inductive reasoning, positing that a universal rule could not be established from an incomplete set of particular instances, thus presaging David Hume’s ‘problem of induction’ about 1500 years later.
Skeptic with a ‘k’
The Romans were great inventors and engineers, but they are not renowned for science or skepticism. On the contrary, they are better known for being superstitious; for instance, the Roman Senate sat only on ‘auspicious days’ thought to be favoured by the gods. They had lots of pseudoscientific beliefs that we skeptics would now regard as quackery or woo. For example, they thought that cabbage was a cure for many illnesses; and in around 78CE, the Roman author Pliny the Elder wrote: ‘I find that a bad cold in the head clears up if the sufferer kisses a mule on the nose’.
So I cannot see any valid historical reason for us to switch from the early Greek spelling of ‘skeptic’ to the Romanised ‘sceptic’. Yes, I know that ‘skeptic’ is the American spelling and ‘sceptic’ is the British spelling, but I don’t think that alters anything. The most likely explanation is that the Americans adopted the spelling of the early Greeks and the British adopted that of the Romans.
Modern philosophical skepticism
Somewhat counter intuitively, the term ‘modern philosophy’ is used to distinguish more recent philosophy from the ancient philosophy of the early Greeks and the medieval philosophy of the Christian scholastics. Thus ‘modern philosophy’ dates from the Renaissance of the 14th to the 17th centuries, although precisely when modern philosophy started within the Renaissance period is a matter of some scholarly dispute.
The defining feature of modern philosophical skepticism is the questioning the validity of some or all types of knowledge. So before going any further, we need to define knowledge.
The branch of philosophy dealing with the study of knowledge is called ‘epistemology’. The ancient philosopher Plato famously defined knowledge as ‘justified true belief’, as illustrated by the Venn diagram below. According to this definition, it is not sufficient that a belief is true to qualify as knowledge – a belief based on faith or even just a guess could happen to be true by mere coincidence. So we need adequate justification of the truth of the belief for it to become knowledge. Although there are a few exceptions, known as ‘Gettier problems’, this definition of knowledge is still largely accepted by modern philosophers, and will do for our purposes here. (Epistemology is mainly about the justification of true beliefs rather than this basic definition of knowledge).
There are also different types of knowledge that are relevant to this discussion.
A priori knowledge is knowledge that is known independently of experience. For instance, we know that ‘all crows are birds’ without having to conduct an empirical survey of crows to investigate how many are birds and whether there are any crows that are not birds. Crows are birds by definition – it is just impossible for there to be an animal that is a crow but is not a bird.
On the other hand, a posteriori knowledge is knowledge that is known by experience. For instance, we only know that ‘all crows are black’ from empirical observations of crows. It is not impossible that there is a crow that is not black, for example as a result of some genetic mutation.
The above distinction illustrates how not all knowledge needs to be empirical. Indeed, one of the earliest modern philosophers and skeptics, Rene Descartes (1596-1650) was a French mathematician, scientist and philosopher. (His name is where the mathematical word ‘Cartesian’ comes from). These three interests of his were interrelated, in the sense that he had a mathematical and scientific approach to his philosophy. Mathematics ‘delighted him because of its certainty and clarity’. His fundamental aim was to attain philosophical truth by the use of reason and logical methods alone. For him, the only kind of knowledge was that of which he could be certain. His ideal of philosophy was to discover hitherto uncertain truths implied by more fundamental certain truths, in a similar manner to mathematical proofs.
Using this approach, Descartes engaged in a series of meditations to find a foundational truth of which he could be certain, and then to build on that foundation a body of implied knowledge of which he could also be certain. He did this in a methodical way by first withholding assent from opinions which are not completely certain, that is, where there is at least some reason for doubt, such as those acquired from the senses. Descartes concludes that one proposition of which he can be certain is ‘Cogito, ergo sum’ (which means ‘I think, therefore I exist’).
In contrast to Descartes, a different type of philosophical skeptic David Hume (1711-1776) held all human knowledge is ultimately founded solely in ‘experience’. In what has become known as ‘Hume’s fork’, he held that statements are divided up into two types: statements about ideas are necessary statements that are knowable a priori; and statements about the world, which are contingent and knowable a posteriori.
In modern philosophical terminology, members of the first group are known as analytic propositions and members of the latter as synthetic propositions. Into the first class fall statements such as ‘2 + 2 = 4’, ‘all bachelors are unmarried’, and truths of mathematics and logic. Into the second class fall statements like ‘the sun rises in the morning’, and ‘the Earth has precisely one moon’.
Hume tried to prove that certainty does not exist in science. First, Hume notes that statements of the second type can never be entirely certain, due to the fallibility of our senses, the possibility of deception (for example, the modern ‘brain in a vat’ hypothesis) and other arguments made by philosophical skeptics. It is always logically possible that any given statement about the world is false – hence the need for doubt and skepticism.
Hume formulated the ‘problem of induction’, which is the skeptical question of whether inductive reasoning leads to knowledge understood in the classic philosophical sense. This problem focuses on the alleged lack of justification for generalising about the properties of a class of objects based on some number of observations of particular instances of that class (for example, the inference that ‘all swans we have seen are white, and therefore, all swans are white’, before the discovery of black swans in Western Australia).
Immanuel Kant (1724-1804) was (and still is) a major philosophical figure who tried to show the way beyond the impasse which modern philosophy had led to between rationalists such as Descartes and empiricists such as Hume. Kant is widely held to have synthesised these two early modern philosophical traditions. And yet he was also a skeptic, albeit of a different variety. Kant thought that only knowledge gained from empirical science is legitimate, which is a forerunner of modern scientific skepticism. He thought that metaphysics was illegitimate and largely speculative; and in that sense he was a philosophical skeptic.
In 1924, the Spanish philosopher Miguel de Unamuno disputed the common dictionary definition of skepticism. He argued that ‘skeptic does not mean him who doubts, but him who investigates or researches as opposed to him who asserts and thinks that he has found’. Sounds familiar, doesn’t it?
Modern scientific skepticism is different from philosophical skepticism, and yet to some extent was influenced by the ideas of Pyrrho of Elis, David Hume, Immanuel Kant and Miguel de Unamuno.
Most skeptics in the English-speaking world see the 1976 formation of the Committee for the Scientific Investigation of Claims of the Paranormal (CSICOP) in the United States as the ‘birth of modern skepticism’. (CSICOP is now called the Committee for Skeptical Inquiry – CSI). However, CSICOP founder and philosophy professor Paul Kurtz has said that he actually modelled it after the Belgian Comité Para of 1949. The Comité Para was partly formed as a response to a predatory industry of bogus psychics who were exploiting the grieving relatives of people who had gone missing during the Second World War.
Kurtz recommended that CSICOP focus on testable paranormal and pseudoscientific claims and to leave religious aspects to others. CSICOP popularised the usage of the terms ‘skeptic’, ‘skeptical’ and ‘skepticism’ by its magazine, Skeptical Inquirer, and directly inspired the foundation of many other skeptical organizations throughout the world, including the Australian Skeptics in 1980.
Through the public activism of groups such as CSICOP and the Australian Skeptics, the term ‘scientific skepticism’ has come to symbolise an activist movement as well as a type of applied philosophy.
There are several definitions of scientific skepticism, but the two that I think are most apt are those by the Canadian skeptic Daniel Loxton and the American skeptic Steven Novella.
Daniel Loxton’s definition is ‘the practice or project of studying paranormal and pseudoscientific claims through the lens of science and critical scholarship, and then sharing the results with the public.’
Steven Novella’s definition is ‘scientific skepticism is the application of skeptical philosophy, critical thinking skills, and knowledge of science and its methods to empirical claims, while remaining agnostic or neutral to non-empirical claims (except those that directly impact the practice of science).’ By this exception, I think he means religious beliefs that conflict with science, such as creationism or opposition to stem cell research.
In other words, scientific skeptics maintain that empirical investigation of reality leads to the truth, and that the scientific method is best suited to this purpose. Scientific skeptics attempt to evaluate claims based on verifiability and falsifiability and discourage accepting claims on faith or anecdotal evidence. This is different to philosophical skepticism, although inspired by it.
Descartes, R. (1641) Meditations on First Philosophy: With Selections from the Objections and Replies, trans. and ed. John Cottingham, Cambridge: Cambridge University Press.
Hume, David.(1748) An Enquiry Concerning Human Understanding . Gutenberg Press.
Kant, Immanuel (1787) Critique of Pure Reason 2nd edition. Cambridge: Cambridge University Press.
Loxton, Daniel. (2013) Why Is There a Skeptical Movement? (PDF). . Retrieved 12 January 2017.
Novella, Steven (15 February 2013). ‘Scientific Skepticism, Rationalism, and Secularism’. Neurologica (blog). Retrieved 12 February 2017.
Russell, Bertrand. (1961) History of Western Philosophy. 2nd edition London: George Allen & Unwin.
Unamuno, Miguel de., (1924) Essays and soliloquies London: Harrap.
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