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13. Knowledge Criteria / B. Internal Justification / 3. Evidentialism / a. Evidence

[experiences and facts pointing towards knowledge]

17 ideas
People dislike believing without evidence, and try to avoid it [Reid]
     Full Idea: To believe without evidence is a weakness which every man is concerned to avoid, and which every man wishes to avoid.
     From: Thomas Reid (Essays on Intellectual Powers 2: Senses [1785], 20)
     A reaction: It seems to be very common, though, for people to believe things on incredibly flimsy evidence, if they find the belief appealing. This is close to Clifford's Principle, but not quite as dogmatic.
Scientists will give up any conclusion, if experience opposes it [Peirce]
     Full Idea: The scientific man is not in the least wedded to his conclusions. He risks nothing upon them. He stands ready to abandon one or all as experience opposes them.
     From: Charles Sanders Peirce (Reasoning and the Logic of Things [1898], I)
     A reaction: In the age of massive speculative research grants, the idea that 'he risks nothing upon them' is no longer true. Ditto for building aircraft and bridges, which are full of theoretical science. Notoriously, many scientists don't live up to Peirce's idea.
I simply reject evidence, if it is totally contrary to my web of belief [Smart]
     Full Idea: The simplest way of fitting the putative observed phenomena of telepathy or clairvoyance into my web of belief is to refuse to take them at face value.
     From: J.J.C. Smart (Explanation - Opening Address [1990], p.07-8)
     A reaction: Love it. It is very disconcerting for the sceptical naturalist to be faced with adamant claims that the paranormal has occurred, but my response is exactly the same as Smart's. I reject the reports, no matter how passionately they are asserted.
We don't distinguish between accepting, and accepting as evidence [Harman]
     Full Idea: There is no distinction between what we accept as evidence and whatever else we accept.
     From: Gilbert Harman (Thought [1973], 10.4)
In the medieval view, only deduction counted as true evidence [Hacking]
     Full Idea: In the medieval view, evidence short of deduction was not really evidence at all.
     From: Ian Hacking (The Emergence of Probability [1975], Ch.3)
     A reaction: Hacking says the modern concept of evidence comes with probability in the 17th century. That might make it one of the most important ideas ever thought of, allowing us to abandon certainties and live our lives in a more questioning way.
Formerly evidence came from people; the new idea was that things provided evidence [Hacking]
     Full Idea: In the medieval view, people provided the evidence of testimony and of authority. What was lacking was the seventeenth century idea of the evidence provided by things.
     From: Ian Hacking (The Emergence of Probability [1975], Ch.4)
     A reaction: A most intriguing distinction, which seems to imply a huge shift in world-view. The culmination of this is Peirce's pragmatism, in Idea 6948, of which I strongly approve.
How do we distinguish negative from irrelevant evidence, if both match the hypothesis? [Lipton]
     Full Idea: How can Best Explanation distinguish negative evidence from irrelevant evidence, when the evidence is logically consistent with the hypothesis?
     From: Peter Lipton (Inference to the Best Explanation (2nd) [2004], 05 'A case')
     A reaction: There seems no answer to this other than to assess batches of evidence by their coherence, rather than one at a time. Anomalies can be conclusive, or pure chance.
Absence of evidence proves nothing, and weird claims need special evidence [McGrew]
     Full Idea: Two well know slogans (popularised by Carl Sagan) are 'absence of evidence is not evidence of absence', ...and 'extraordinary claims require extraordinary evidence'.
     From: Timothy McGrew (Evidence [2011], 'Absence')
     A reaction: [Sagan was a popular science writer and broadcaster] The second one is something like Hume's argument against miracles. The old problem of the 'missing link' for human evolution embodied the first idea.
Does spotting a new possibility count as evidence? [McGrew]
     Full Idea: Does the sudden realization of a heretofore unrecognized possibility count as evidence?
     From: Timothy McGrew (Evidence [2011], 'Evid..')
     A reaction: [Nice use of 'heretofore'! Why say 'previously' when you can keep these wonderful old English words alive?] This means that we can imagine new evidence ('maybe the murderer was a snake'!). Wrong. The evidence is what suggests the possibility.
Every event is highly unlikely (in detail), but may be perfectly plausible [McGrew]
     Full Idea: At a certain level of detail, almost any claim is unprecedented. How likely is 'Matilda won at Scrabble on Thursday with a score of 438 while drinking mint tea'? But there is nothing particularly unbelievable about the claim.
     From: Timothy McGrew (Evidence [2011], 'Extraordinary')
     A reaction: A striking idea, which rules out the simplistic idea that we can just assess evidence by its isolated likelihood. Context is crucial. How good is 438? What if she smoked opium? What if there is no Scrabble set on her island?
Criminal law needs two separate witnesses, but historians will accept one witness [McGrew]
     Full Idea: An ancient rule in law is that a criminal conviction needs evidence of two independent witnesses, but in history it is assumed that a document deserves the benefit of the doubt if it cannot be independently verified.
     From: Timothy McGrew (Evidence [2011], 'Interp..')
     A reaction: [compressed; McGrew's full account qualifies it a bit] A nice observation. One might even be suspicious of the two 'independent' witnesses, if there were lots of other reasons to doubt someon's guilt. A single weird document is also dubious.
Maybe all evidence consists of beliefs, rather than of facts [McGrew]
     Full Idea: Some philosophers have been attracted to the view that, strictly speaking, what counts as evidence is not a set of physical objects or even experiences, but rather a set of believed propositions.
     From: Timothy McGrew (Evidence [2011], 'Prop..')
     A reaction: This may be right. However, as always, I think animals are a key test. Do animals respond to evidence? Even if they did, they might need to 'make sense' of what they experienced, and even formulate a non-linguistic proposition.
If all evidence is propositional, what is the evidence for the proposition? Do we face a regress? [McGrew]
     Full Idea: Taking evidence as propositional may trade one problem for another. If the bloodstain isn't evidence, but 'this is a bloodstain' is evidence, then what serves as evidence for the belief about the bloodstain? Is there an infinite regress?
     From: Timothy McGrew (Evidence [2011], 'Prop..')
     A reaction: [compressed] I quite like evidence being propositional, but then find this. I'll retreat to my beloved coherence. I do not endorse Sellars's 'only a belief can justify a belief', because raw experience has to be part of what is coherent.
Several unreliable witnesses can give good support, if they all say the same thing [McGrew]
     Full Idea: The testimony of a number of independent witnesses, none of them particularly reliable, who give substantially the same account of some event, may provide a strong argument in its favor.
     From: Timothy McGrew (Evidence [2011], 'Testimonial')
     A reaction: A striking point. It obviously works well for panicking people in a crowd during an incident. Does it also apply to independent scientists who are known to cheat? They may not collaborate, but may all want the same result.
Clifford's dictum seems to block our beliefs in morality, politics and philosophy [Bayne]
     Full Idea: Endorsing Clifford's dictum threatens to undermine our right to hold many of our most cherished beliefs about morality, politics, and philosophy, for these are domains in which it is notoriously difficult to secure consensus.
     From: Tim Bayne (Thought: a very short introduction [2013], Ch.7)
     A reaction: I would say that those beliefs are amenable to evidence, but the evidence is often highly generalised, which is what makes those subjects notoriously difficult. The existence of a convention is a sort of evidence.
How we evaluate evidence depends on our background beliefs [Bayne]
     Full Idea: A claim that might be very plausible given one set of background beliefs might be highly implausible when evaluated in the light of a different set of background beliefs.
     From: Tim Bayne (Thought: a very short introduction [2013], Ch.7)
In English 'evidence' is a mass term, qualified by 'little' and 'more' [Rumfitt]
     Full Idea: In English, the word 'evidence' behaves as a mass term: we speak of someone's having little evidence for an assertion, and of one thinker's having more evidence than another for a claim. One the other hand, we also speak of 'pieces' of evidence.
     From: Ian Rumfitt (The Boundary Stones of Thought [2015], 5.2)
     A reaction: And having 'more' evidence does not mean having a larger number of pieces of evidence, so it really is like an accumulated mass.