Throughout most of the 20th century, the medical community knew that large amounts of stress causes stomach ulcers—or at least they though they did. Here are some "known facts" (things that doctors thought were true) prior to 1979 about ulcers:
But then, in the 1980s an Australian physician Dr. Barry Marshall, convinced that the medical community had it all wrong, infected himself with what he believed to be the real culprit responsible for the disease, H. pylori. In order to prove his theories against the overwhelming consensus, Marshall famously drank the bacteria in question.
And as it turns out, he was absolutely right. We now know that peptic ulcer disease is actually caused by bacterial infection.
Often, when people tell this story, they say things like "Everyone knew that stress caused ulcers, before an Australian doctor in the early 1980s proved that ulcers are actually caused by bacteria." But as philosophers we might wonder what we should make of this kind of claim. Did the doctors really know that stress was causing the ulcers or did they only think they knew it? Or phrased a bit more generally by Socrates “If one fails to get at the truth of a thing, will he ever be a person who knows that thing?” The resulting dialogue in Plato’s Theatetus reveals his interlocutor’s answer (186c-187b). Knowledge cannot be mere opinion, because there may be a false opinion. And the answer contemporary philosophers give has changed little since. Basically every epistemic analysis today includes a truth condition for knowledge. It’s just overwhelmingly clear to philosophers that only true things can be known.
Nonetheless, there seem to be several examples today showing that non-philosophers do not find this thesis obvious, and that at least as far as ordinary language is concerned, people frequently use ‘know’ in what appear to be blatantly non-factive ways. A quick Google search--from the ulcer case, to headlines in the New York Times, to major blockbuster movies--reveals that non-factivity may be all around us!
Examples like these have led a growing number of philosophers to begin to speculate about the role of factivity in the actual knowledge judgments people make, as well as the significance these ordinary judgments might have for traditional epistemic theorizing. John Turri for instance, has advanced a performance-view of knowledge that allows for knowledge of “approximate truths”, which are strictly speaking, false beliefs (2011; forthcoming). Sympathy for non-factivity has been expressed in research by Daniel Nolan (2008). And, the possibility that epistemic contextualism might allow for contexts under which certain kinds of false beliefs qualify as knowledge has also been (at least) discussed in the works of Keith DeRose (2009).
And perhaps the most comprehensive challenge against orthodoxy to date is presented by Allan Hazlett. In two recent papers, “The Myth of Factive Verbs,” and “Factive Presupposition and the Truth Condition on Knowledge” Hazlett displays compelling evidence that people ordinarily use purportedly factive verbs like ‘know’, ‘learn’, ‘remember’, and ‘realize’ in utterances of the form ‘S knows that p’ in ways that frequently do NOT require that p is true. Hazlett’s theory is that these kinds of sentences are acceptable to non-philosophers because the folk concept underlying the meaning of ‘knows’ allows that false things can genuinely be known.
But given that a number of epistemologists have begun to focus more on the truth condition in light of intuitions about ordinary usage, we may wonder, could it really be that the folk concept of knowledge is truly a non-factive concept? Afterall, if true, it seems this would have a series of important epistemic and methodological implications about the connection between the ordinary concept and the (decidedly factive) concept of knowledge philosophers have historically been interested in analyzing.
Besides non-factivity however, another possible explanatory hypothesis of these linguistic data (like the ulcer case) is that ordinary uses of ‘knows’ are highly sensitive to something called ‘protagonist projection’. The basic idea basic idea is that non-factive uses frequently might just appear acceptable to us only because we take up the protagonist’s perspective and say what seems true from their perspective--and not because people think it's actually possible to know false things. (This is kind of like when one talks about someone else, and—with sufficient cues, e.g. imitating their bodily language and tone of voice—can then use ‘I’ to refer to this other person.)
To prove that Experimental Philosophy isn’t always about attacking the great tradition, I went ahead and ran some experiments attempting to confirm armchair intuitions about the factivity of ‘knows’. A draft of the paper is available HERE. The main goal of these experiments was to use explicit paraphrasing tasks (a method pioneered in the study of mental state attributions to groups) to see if the linguistic evidence about factivity collected so far is better explained by (i) the folk tendency to adopt the perspective of the putative ‘knower’ via protagonist projection when attributing knowledge to falsehoods or (ii) an underlying folk concept which really does allow for knowledge of false things.
In the paper above, there's work looking at the ulcer case, as well as some other examples from the web and from movies. However, here is another experiment from the paper looking specifically at the role of false complement clauses on people's knowledge judgments. In a 2 (truth) x 4 (verb) between-subjects design, participants (N = 217, 102 men, median age = 34) were presented with the following story about two police offers relaying some testimony. While each participant only saw one story, the stories varied by the verb used in bold (‘know’, ‘learned’, ‘realized’, or ‘believe’). Below is an example of the vignette involving ‘knows’:
Officer Ted asks the Police Sergeant, “Is there any information from the FBI about how the bomb was constructed?”
The Sergeant told him, “From the investigation, they know the bomb was homemade.”
After seeing one vignette, roughly half of participants were presented with a complement phrase expressing a false proposition.
False Complement: But actually, the bomb in question only appeared homemade. Instead, professionals constructed it in a high-tech chemical plant.
The other half received a complement expressing a true proposition:
True Complement: And as it turns out, the bomb in question was homemade. Non-professionals had constructed it in a basement apartment.
They were then asked to select one of the explicit paraphrases provided regarding the usage of that verb (order of these answer choices randomized in all experiments):
Which of the following do you think best describes what is meant in the BOLD portion of the above sentence:
A) The FBI thought they knew (projectionist answer)
B) The FBI really did know (non-factive answer)
If participants are reading these sentences and interpreting the verbs ‘know’, ‘learned’, ‘realized’ as factive, then we would expect them to be more likely to adopt the projectionist answer in false complement cases—that from protagonist x’s perspective, ‘x thought that x Φ’. Alternatively, if the sentences really are rightly interpreted as counterexamples to Factivity, then we would expect participants to give the non-factive answer—that from the participant’s more informed perspective, “x really did Φ.” We would also expect a null effect for ‘believes’, whereby the truth or falsity of the complement still results in a majority of non-factive answers (and of course, high “x really did Φ” answers for all verbs in the true complement conditions).
And that was exactly what was found. Most participants gave the ‘really Φ’ answer for ‘know’ (86%), ‘learn’ (78%), ‘realize’ (90%), and ‘believe’(80%) when presented with the true complements. But participants were significantly less likely to give the ‘really Φ’ answer for all factive verbs in false complement cases: 12%, 21%, and 31%, respectively. And as expected, the false complement case had no significant effect on judgments about ‘believe’ (61%). Lastly, the difference between projectionist answers in all the factive verb sentences compared to the ‘believe’ sentences—within just those cases with false complements—continues to be significant:
So one interpretation is that these data begin to call into question whether people’s treatment of these particular sentences really is best interpreted as a counterexample to Factivity. On the other hand, it looks like people may be engaging in projective readings, rather than actually attributing knowledge to subjects with false beliefs.
Of course, the data (here and throughout the paper above) do not show that all would-be non-factive uses of ‘know’ are cases of protagonist projection. Nor do they show that there cannot be evidence against factivity independently of projection phenomena. What they do suggest however is that absent strong evidence in favor of the non-factive concept, orthodoxy must still stand. In the meantime, it looks as though the folk concept might be more closely related to the philosophical one (regarding knowing false things) after all. Or as Joe Friday used to say, when it comes to knowledge perhaps “All we know are the facts, ma'am”.
So we might conclude that without further evidence to the contrary, the data suggest that philosophers who choose to justify provisions of factivity in their philosophical analyses of knowledge by appeal to the ordinary usage or the ordinary concept of knowledge now have empirically supported reasons for doing so. And--perhaps more importantly--we might also conclude that this result serves to highlight the need for more empirically informed research in epistemology when making inferences about ordinary concepts or language practices.