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13. Knowledge Criteria / D. Scepticism / 1. Scepticism

[general doubts about the possibility of knowledge]

33 ideas
If we succeed in speaking the truth, we cannot know we have done it [Xenophanes]
     Full Idea: No man has seen certain truth, and no man will ever know about the gods and other things I mentioned; for if he succeeds in saying what is fully true, he himself is unaware of it; opinion is fixed by fate on all things.
     From: Xenophanes (fragments/reports [c.530 BCE], B34), quoted by Sextus Empiricus - Against the Professors (six books) 7.49.4
Protagoras was the first to claim that there are two contradictory arguments about everything [Protagoras, by Diog. Laertius]
     Full Idea: Protagoras was the first to claim that there are two contradictory arguments about everything.
     From: report of Protagoras (fragments/reports [c.441 BCE], A01) by Diogenes Laertius - Lives of Eminent Philosophers 09.51
Cratylus decided speech was hopeless, and his only expression was the movement of a finger [Cratylus, by Aristotle]
     Full Idea: Cratylus thought speech of any kind was radically inappropriate and that expression should be restricted exclusively to the movement of the finger.
     From: report of Cratylus (fragments/reports [c.425 BCE]) by Aristotle - Metaphysics 1010a
Democritus says there is either no truth, or it is concealed from us [Democritus, by Aristotle]
     Full Idea: Democritus concludes that either there is no truth or it is concealed from us.
     From: report of Democritus (fragments/reports [c.431 BCE], A112) by Aristotle - Metaphysics 1009b12
We actually know nothing, and opinions are mere flux [Democritus]
     Full Idea: Certainly this argument too makes it clear that in reality [eteé] we know nothing about anything, but for each person opinion is a rhythmic afflux [epirhusmié].
     From: Democritus (fragments/reports [c.431 BCE], B007), quoted by Sextus Empiricus - Against the Logicians (two books) 7.137
     A reaction: This seems to pick 'all is flux' up from Heraclitus, and make Democritus (along with aspects of Socrates) the true source of ancient scepticism.
We in fact know nothing, but we each restructure our reality with beliefs [Democritus]
     Full Idea: In reality we know nothing about anything, but belief restructures things for each of us.
     From: Democritus (fragments/reports [c.431 BCE], B007), quoted by Sextus Empiricus - Against the Professors (six books) 7.136
It is obviously impossible to understand the reality of each thing [Democritus]
     Full Idea: It will be obvious that it is impossible to understand how in reality each thing is.
     From: Democritus (fragments/reports [c.431 BCE], B008), quoted by Sextus Empiricus - Against the Professors (six books) 7.137
We know nothing in reality; for truth lies in an abyss [Democritus]
     Full Idea: We know nothing in reality; for truth lies in an abyss.
     From: Democritus (fragments/reports [c.431 BCE], B117), quoted by Diogenes Laertius - Lives of Eminent Philosophers 09.72.10
There can't be any knowledge if things are constantly changing [Plato]
     Full Idea: It isn't even reasonable to say that there is such a thing as knowledge, Cratylus, if all things are passing on and none remain.
     From: Plato (Cratylus [c.377 BCE], 440a)
     A reaction: This encapsulates Plato's horror at Heraclitus scepticism about the stable identity of things. It leads to the essentialism of Aristotle and Leibniz, who fear that there is no knowledge if we can't pin down individual identities. Know processes?
Anaxarchus said that he was not even sure that he knew nothing [Anaxarchus, by Diog. Laertius]
     Full Idea: Anaxarchus said that he was not even sure that he knew nothing.
     From: report of Anaxarchus (fragments/reports [c.340 BCE]) by Diogenes Laertius - Lives of Eminent Philosophers 09.10.1
The Pyrrhonians attacked the dogmas of professors, not ordinary people [Pyrrho, by Fogelin]
     Full Idea: The attacks of the Pyrrhonian sceptics are directed against the dogmas of the 'professors', not against the beliefs of the common people pursuing the business of daily life.
     From: report of Pyrrho (reports [c.325 BCE]) by Robert Fogelin - Walking the Tightrope of Reason Ch.4
     A reaction: This may be because they thought that ordinary people were too confused to be worth attacking, rather than because they lived in a state of beautifully appropriate beliefs. Naïve realism is certainly worth attacking.
Epicurus denied knowledge in order to retain morality or hedonism as the highest values [Nietzsche on Epicurus]
     Full Idea: Epicurus denied the possibility of knowledge in order to retain moral (or hedonistic) values as the highest values.
     From: comment on Epicurus (fragments/reports [c.289 BCE]) by Friedrich Nietzsche - The Will to Power (notebooks) §578
     A reaction: The history of philosophy suggests that this dichotomy is unnecessary. Dogmatist place a high value on multitudes of things.
The basis of scepticism is the claim that every proposition has an equal opposing proposition [Sext.Empiricus]
     Full Idea: The main basic principle of the sceptic system is that of opposing to every proposition an equal proposition.
     From: Sextus Empiricus (Outlines of Pyrrhonism [c.180], I.12)
Scepticism has two dogmas: that nothing is definable, and every argument has an opposite argument [Diog. Laertius]
     Full Idea: Sceptics actually assert two dogmas: that nothing should be defined, and that every argument has an opposite argument.
     From: Diogenes Laertius (Lives of Eminent Philosophers [c.250], 9.Py.11)
Sceptics say there is truth, but no means of making or testing lasting judgements [Montaigne]
     Full Idea: Pyrrhonians say that truth and falsehood exist; within us we have means of looking for them, but not of making any lasting judgements: we have no touchstone.
     From: Michel de Montaigne (Apology for Raymond Sebond [1580], p.0564)
     A reaction: This states the key difference between sceptics and relativists. The latter are more extreme as they say there is no such thing as truth. The former concede truth, and their scepticism is about the abilities of human beings. I am an anti-relativist.
Descartes can't begin again, because sceptics doubt cognitive processes as well as beliefs [Pollock/Cruz on Descartes]
     Full Idea: Descartes' strategy of starting over will not work, because the skeptic is not just questioning our beliefs, he is also questioning the cognitive processes by which we arrive at our beliefs, and if we start all over again we use the same processes.
     From: comment on René Descartes (Meditations [1641], §1) by J Pollock / J Cruz - Contemporary theories of Knowledge (2nd)
     A reaction: Scepticism comes in degrees, so there is not one strategy employed by sceptics. It is certainly true, though, that nothing can resist extreme scepticism. The most extreme view is to refuse to accept the meaningfulness of all belief language.
Even if my body and objects are imaginary, there may be simpler things which are true [Descartes]
     Full Idea: Perhaps even though general things like eyes could be imaginary, still one must admit that certain other things that are even more simple and universal are true.
     From: René Descartes (Meditations [1641], §1.20)
Light takes time to reach us, so objects we see may now not exist [Leibniz]
     Full Idea: Since rays of light need time - however little - to reach us, it is possible that the object should be destroyed during the interval and no longer exist when the light reaches the eye.
     From: Gottfried Leibniz (New Essays on Human Understanding [1704], 2.09)
     A reaction: This is the well know 'time lag' argument. Leibniz is no sceptic, but he can hardly fail to accept the truth of this problem. It seems self-evident that stars we observe may no longer exist, although special relativity confuses that issue.
Reason can never show that experiences are connected to external objects [Hume]
     Full Idea: Reason can never find any convincing argument from experience to prove that perceptions are connected with any external objects.
     From: David Hume (Enquiry Conc Human Understanding [1748], XII.I.121)
Mitigated scepticism draws attention to the limitations of human reason, and encourages modesty [Hume]
     Full Idea: A mitigated scepticism … can make dogmatical reasoners become sensible of the strange infirmities of human understanding, and inspire them with more modesty and reserve.
     From: David Hume (Enquiry Conc Human Understanding [1748], XII.III.129)
Kant thought he had refuted scepticism, but his critics say he is a sceptic, for rejecting reality [O'Grady on Kant]
     Full Idea: Kant believed he had given a decisive answer to traditional scepticism, since we can no longer be mistaken about objects, but his critics say he is a sceptic, because he relinquishes our grasp of independent things.
     From: comment on Immanuel Kant (Critique of Pure Reason [1781]) by Paul O'Grady - Relativism Ch.3
     A reaction: A simple issue to raise about the man, my first reaction being that he is a sceptic. He says the 'noumenon' (true reality) is unknowable, but I say we can meaningfully speculate and theorise about it.
Our knowledge is illogical, because it rests on false identities between things [Nietzsche]
     Full Idea: Every piece of knowledge that is beneficial to us involves an identification of nonidentical things, of things that are similar, which means that it is essentially illogical.
     From: Friedrich Nietzsche (Unpublished Writings 1872-74 [1873], 19 [236])
     A reaction: I take the thought to be that no two tigers are alike, but we call them all 'tigers' and merge them into a type, and then all our knowledge is based on this distortion. A wonderful idea. I love particulars You should love particulars.
The most extreme scepticism is when you even give up logic [Nietzsche]
     Full Idea: Even skepticism contains a belief: the belief in logic. The most extreme position is hence the abandoning of logic.
     From: Friedrich Nietzsche (Unpublished Writings 1872-74 [1873], 29 [008])
     A reaction: Some might say that flirting with non-classical logic (as in Graham Priest) is precisely travelling down this road. You could also be sceptical about meaning in language, so you couldn't articulate your abandonment of logic.
Doubts can't exist if they are inexpressible or unanswerable [Wittgenstein]
     Full Idea: Doubt can exist only where a question exists, a question only where an answer can exist, and an answer only where something can be said.
     From: Ludwig Wittgenstein (Tractatus Logico-Philosophicus [1921], 6.51)
     A reaction: I don't agree with any of that. It is typical of the phase when philosophers were mesmerised by language. Cats look puzzled sometimes. A glimmering of doubt may be pre-linguistic, inexpressible and unanswerable, but still feels like a doubt.
Maybe billions of changeless years have elapsed since my last meal [Shoemaker]
     Full Idea: If it is possible for there to be changeless intervals of time, then it may seem compatible with my total experience that any number of such intervals, each of them lasting billions of years, should have elapsed since I ate my last meal.
     From: Sydney Shoemaker (Time Without Change [1969], p.52)
     A reaction: Compare Idea 2792. A nice new sceptical thought! Shoemaker's paper is devoted, successfully I think, to proving that there can indeed by changless intervals of time.
Protagoras says arguments on both sides are always equal [Kim, by Seneca]
     Full Idea: Protagoras declares that it is possible to argue either side of any question with equal force, even the question whether or not one can equally argue either side of any question!
     From: report of Jaegwon Kim (Mind in a Physical World [1998]) by Seneca the Younger - Letters from a Stoic 088
     A reaction: This is perhaps the most famous sceptical argument in the ancient world (though, note, Protagoras is most famous for his relativism rather than his scepticism). It is, of course, wrong. The arguments are sometimes equal, but often they are not.
There are two contradictory arguments about everything [Kim]
     Full Idea: There are two contradictory arguments about everything.
     From: Jaegwon Kim (Mind in a Physical World [1998], B06a), quoted by (who?) - where?
No one knows anything, and no one is ever justified or reasonable [Unger]
     Full Idea: I argue for the thesis that no one ever knows about anything, ...and that consequently no one is ever justified or at all reasonable in anything.
     From: Peter Unger (Ignorance: a Case for Scepticism [1975], Intro)
     A reaction: The premiss of his book seems to be that knowledge is assumed to require certainty, and is therefore impossible. Unger has helped push us to a more relaxed and fallibilist attitude to knowledge. 'No one is reasonable' is daft!
Without confidence in our beliefs, how should we actually live? [Tuck]
     Full Idea: The central question for sceptics is if we lose confidence in the truth of most existing beliefs, then how do we actually live?
     From: Richard Tuck (Hobbes [1989], Ch.4)
     A reaction: Scepticism is not, of course, all or nothing. You can lead a 'normal' life in a virtual reality machine. I find it much more of a struggle to live if I lose faith in values, than if I lose faith in tables.
Scepticism just reveals our limited ability to explain things [Williams,M]
     Full Idea: All the sceptic's arguments show is that there are limits to our capacity to give reasons or cite evidence.
     From: Michael Williams (Problems of Knowledge [2001], Ch.13)
Scepticism about reality is possible because existence isn't part of appearances [McGinn]
     Full Idea: Scepticism about the external world is possible because you can never build existence into the appearances, so it must always be inferred or assumed.
     From: Colin McGinn (Logical Properties [2000], Ch.2)
     A reaction: When McGinn's claim that existence is a very universal property begins to produce interesting observations like this, I think we should take it very seriously.
We assess error against background knowledge, but that is just what radical scepticism challenges [Pritchard,D]
     Full Idea: When faced with an error-possibility we can appeal to background knowledge, as long as the error-possibility does not call into question this background knowledge. The same is not true when we focus on the radical sceptical hypothesis.
     From: Duncan Pritchard (Epistemological Disjunctivism [2012], 2.§5)
     A reaction: [reworded] Doubting everything simultaneously just looks like a mad project. If you doubt linguistic meaning, you can't even express your doubts.
A toper who spies in the distance... [Sommers,W]
     Full Idea: A toper who spies in the distance,/ Striped tigers, will get some assistance/ From reading Descartes,/ Who holds that it's part/ Of his duty to doubt their existence. ... [Leslie Johnson] - (continued in 12402)
     From: Will Sommers (talk [2019])