On Jennifer Lackey’s ‘Testimonial Knowledge and Transmission’

by Tim Harding

In her paper ‘Testimonial Knowledge and Transmission’ Jennifer Lackey (2008: 855-867) argues against the following two theses regarding the justification of testimonial knowledge:

2. For every speaker S and hearer H, if H comes to know that p via S’s testifying that p, then S must know that p.

2*. For every testimonial chain of knowledge C, in order for a hearer H in C to come to know that p via the testimony of a speaker S in C, at least the first speaker S in C must know that p (in some non-testimonial way).

This essay examines Lackey’s critique of thesis 2*, where I argue that Lackey does make out a satisfactory case for her position against it; but that her case is an ‘exception to the rule’ in a similar way that ‘Gettier cases’ are an exception to the rule that knowledge is justified true belief.

To assist in understanding Jennifer Lackey’s position, I shall commence with some brief background information on the role of testimonial knowledge in epistemology; and then I shall provide some definitions of relevant key terms.

Our knowledge can be derived from several different sources: our own direct perceptions of the world, the deductions or inferences we draw from premises, the inductive generalisations we make from numbers of particular instances, our memories, introspection or what philosophers call ‘testimony’.  Testimony in this sense need not be formal testimony in a courtroom or legal document, but what happens whenever one person tells something to someone else (Green 2017: 2).  In a later paper, Lackey (2011: 1) notes that almost everything we know depends in some way or other on the testimony of others.

Lackey (2011: 2-3) draws a distinction between testimony and non-informational expressions of thought or emotion, such as the conversation filler ‘Isn’t it a lovely day?’  Audi (1997: 405) makes a similar point about the statement ‘Ah, what a magnificent tree!’ Lackey provides a more precise account of the nature of testimony as ‘a speaker’s making an act of communication – which includes statements, nods, pointing and so on – that is intended to convey information that p or is taken as conveying the information that p’ (Lackey 2011: 3).  It should be noted here that by the words ‘is taken as’ Lackey assigns an important role in the act of communication to the hearer as well as the speaker.  She also draws a distinction between obtaining information from perception whilst a speaker is speaking (or singing).  For instance, if a person sings ‘I have a soprano voice’ in a soprano voice, the hearer obtains information from aural perception as well as testimony (Lackey 2011: 3).

The next thing we need to distinguish is the difference between reductionist and non-reductionist views about how hearers acquire justified beliefs from the testimony of speakers.  According to reductionists, whose historical roots are traced to the work of David Hume, hearers must also possess non-testimonially based positive reasons in order to be justified in accepting the testimony of speakers (Lackey 2011: 3).  In other words, testimony must ultimately be based on or reduced to other sources such as sense perception, deduction, induction, introspection or memory.  Testimony does not generate any new knowledge – it merely transmits it from another source.  In contrast, non-reductionists consider that testimony is a basic source of justification, on an epistemic par with sense perception, deduction, induction and the like (Lackey 2011: 4).  Non-reductionists maintain that as long as there are no relevant undefeated defeaters, hearers can be justified in accepting what they are told merely on the basis of the testimony of speakers (Lackey 2011: 4).

In her earlier work (the subject of this essay), Lackey (2008: 857) identifies three types of defeaters.  Firstly, a doxastic defeater is a proposition D which is believed by speaker S to be true, yet indicates that S’s belief that p is either false or unreliably formed or sustained.  This type of defeater functions by virtue of being believed, regardless of its truth value. Secondly, a normative defeater is a proposition D which S is justified in believing to be true, yet which indicates that S’s belief that p is either false, or unreliably formed or sustained.  This type of defeater functions by virtue of being a proposition that S should believe, given the evidence that is available to S. Thirdly, a factual defeater is a true proposition D such that if D were added to S’s belief system, then S would be no longer be justified in believing that p.  This type of defeater functions by virtue of being a proposition that is factually true.

Lackey (2008: 862) adds that a defeater may itself be either defeated or undefeated, and that defeater-defeaters can also be further defeated, and so on.  Also, defeaters are not necessarily transmitted via testimony (Lackey 2008: 862).  In the case of doxastic defeaters, ‘when one has a defeater D for one’s belief that p which is not itself defeated by another belief, one has what is called an undefeated defeater for one’s belief that p (Lackey 2008: 862).  These points are important ingredients of her position that a hearer can come to know p via a speaker’s testimony that p despite the fact that even the first speaker in the chain fails to know that p.  However, before discussing this position, I shall briefly allude to Lackey’s critique of the related thesis 2, which is that ‘for every speaker S and hearer H, if H comes to know that p via S’s testifying that p, then S must know that p’.  (I shall refer to this thesis again later).

Lackey (2008: 858) provides a hypothetical case example of a teacher Mrs. Smith who is required by her school to include sections on evolutionary theory in her science classes, despite the fact that she is a devout creationist who does not believe what she is teaching.  Because she obtains her curriculum material from reliable sources such as science textbooks, her students come to have knowledge of evolutionary theory via Mrs. Smith’s testimony, despite the fact that Mrs. Smith does not have this knowledge herself (because she does not believe that it is true).  Lackey (2008: 858) draws an analogy here with a Kantian teaching utilitarianism, or an atheist teaching Christianity, and so on.

Turning now to Lackey’s critique of thesis 2*, she provides another case example of Jane, who has an undefeated defeater in the form of a severe sceptical doubt about the truth of all of her beliefs. A passerby, Jim, asks her where the café is and she tells him that it is around the corner (which is true), but does not tell him of her sceptical doubts.  In other words, Jane does not transmit her undefeated doxastic defeater to Jim.  In this way, speakers can have doxastic defeaters that hearers do not have.  Jim does not have any other doxastic defeaters for his ordinary beliefs, one of which is a belief based upon inductive inference that speakers are generally reliable when giving directions.  As Jane gives Jim no reason to doubt her sincerity or competence in giving directions, Jim forms the true belief that there is a café around in the corner on the basis of Jane’s testimony (Lackey 2008: 862-863).

Lackey (2008: 862) argues that given that Jane has an undefeated defeater (her sceptical doubt) that Jim does not have, he not only has knowledge that Jane lacks, but Jane is the first link in the chain of testimonial knowledge in question (a chain need have only two links).  The same argument would apply if there were a longer chain where Jane gave directions to Steve who passed them on to Jim.  Lackey concludes from this case example that a hearer can come to know p via a speaker’s testimony that p despite the fact that even the first speaker in the chain fails to know that p (Lackey 2008: 862).

According to Lackey (2008: 863), there are two different ways in which doxastic defeaters can fail to be transmitted via testimony.  The first way is like the Jane and Jim case above, where a speaker testifies that p but fails to transmit an undefeated defeater D.  The second way is where a speaker testifies that p and reports a defeater D, but the hearer accepts only the information p.  Alternatively, a doxastic defeater could be transmitted via a speaker’s testimony, but the hearer has a defeater for that defeater, thereby enabling the speaker’s testimony to still to impart knowledge to the hearer.  Lackey (2008: 863-864) provides further cases and arguments showing how normative and factual defeaters can perform a similar role to doxastic defeaters in this context.

Finally, Lackey (2008: 865-866) proposes an alternative thesis to 2 and 2* which she claims avoids the problems that she has identified in her paper:

2**. For every speaker S and hearer H, if H comes to know that p via S’s statement that p, then S’s statement that p must be appropriately connected with the fact that p.

Lackey does not specify what kind of connection is appropriate between S’s statement that p and the fact that p.  One instance may be if S’s statement ‘tracks the truth’ in Nozick’s sense (Nozick 2008: 255-258).  That is, if p were not true S would not state that p, and if p were true S would state that p.  Using Lackey’s case example of Jane and Jim, despite Jane’s sceptical doubts, Jane would not have told Jim that the café was around the corner if that was untrue.  If Jane really had no idea where the café was, she would have said so, because that would have been more consistent with her sceptical doubts.

Having outlined Lackey’s position on thesis 2*, I shall now consider some alternative views and objections to it, and then I shall put forward my own view.

Robert Audi (1997: 405-409) speaks of a ‘kind of trust’ where beliefs about the credibility of the speaker her testimony play a mainly filtering role, in terms of the speakers sincerity and competence.  For instance, ‘when trusted friends speak to us on matters we do not think are beyond their competence, we normally just believe what they tell us’ (Audi (1997: 406).  According to Audi (1997: 409) testimony can be a source of basic belief.  In a non-reductionist sense, a testimonially based belief need not derive from other basic beliefs, as discussed earlier.

In his paper ‘Content Preservation’, Tyler Burge (2008: 840-841) identifies what he calls the Acceptance Principle, which he defines and justifies as follows:

A person is a priori entitled to accept as true something that is presented as true and that is intelligible to him, unless there are stronger reasons not to do so, because it is prima facie preserved (received) from a rational source, or resource for reason; reliance on rational sources – or resources for reason – is, other things being equal, necessary to the function of reason.

Burge (2008: 841) argues that one is prima facie entitled to rely on the undefeated rationality of rational beings, although he concedes that this is no guarantee of truth (Burge 2008: 844).  Applying this acceptance principle to Lackey’s Jane and Jim case example, because Jim did not know about Jane’s sceptical doubts, he was entitled prima facie to accept Jane’s directions to the café as being true – he had no stronger reason not to do so.

On the other hand, in her paper ‘Against Gullibility’ Elizabeth Fricker (2008: 815) identifies another argument that a hearer has a presumptive epistemic right to trust an arbitrary speaker, on the grounds that ‘it is not, generally speaking, possible for a hearer to obtain independent confirmation that a given speaker is trustworthy – that what she says will be true’.  Fricker (2008: 826) argues against this thesis by saying that a hearer should always engage in some assessment of the speaker for trustworthiness.  She thinks that to believe what is asserted without doing so amounts to gullibility.  In this way, Fricker is arguing against Lackey’s case example of Jane and Jim – Jim should not have blindly believed Jane’s directions as to where the café was.

My own view is that whilst Lackey has made out a satisfactory case for her position in the Jane and Jim case example (and any other similar cases), her position does not necessarily translate to other cases based on different scenarios.  Take for instance, Lackey’s case example of Mrs. Smith the creationist who is required to teach evolutionary theory.  Whilst I think it is possible that Mrs. Smith could teach evolutionary theory without believing in it and thus knowing about it (Lackey’s argument against thesis 2), I think it is implausible that Lackey’s argument against thesis 2* could apply in this case.  It does not make sense for students to come to know about evolutionary theory unless at least the first person in the chain of testimony (in this case Charles Darwin) also knew about it.  Knowledge about evolutionary theory could not be generated merely via the chain of testimony.  I would also make the point that Lackey’s thesis 2** about being ‘appropriately connected’ would not solve this problem either.  It would not be sufficient to say that Mrs. Smith’s teaching was appropriately connected to evolutionary theory unless it was based on knowledge held by the first person in the testimonial chain, which in this case is Charles Darwin.

For these reasons, I conclude that Lackey’s argument against thesis 2* can satisfactorily apply in some special cases such as the Jane and Jim case, but not in other cases such as the Mrs. Smith case.  I would therefore characterise Lackey’s argument against thesis 2* as ‘an exception to the rule’ rather than a universally applicable argument, in a somewhat similar status to what are known as Gettier problems with the definition of knowledge as justified true belief.


Audi, Robert. (1997) “The Place of Testimony in the Fabric of Knowledge and Justification.” American Philosophical Quarterly 34: 405-22.

Burge, Tyler, (2008) ‘Content Preservation’ in Sosa, E., Kim, J., Fantl, J., and McGrath. M. Epistemology : An Anthology 2nd edition. Carlton: Blackwell. 836-854.

Fricker, Elizabeth, (2008) ‘Against Gullibility’ in Sosa, E., Kim, J., Fantl, J., and McGrath. M. Epistemology : An Anthology 2nd edition 2008. Carlton: Blackwell. 815-835.

Green, Christopher, R. ” Epistemology of Testimony”, The Internet Encyclopedia of Philosophy, ISSN 2161-0002, http://www.iep.utm.edu/ep-testi/, Viewed 17 October 2017.

Lackey, Jennifer, (2008) ‘Testimonial Knowledge and Transmission’ in Sosa, E., Kim, J., Fantl, J., and McGrath. M. Epistemology : An Anthology 2nd edition 2008. Carlton: Blackwell. 855-867.

Lackey, Jennifer, (2011) ‘Testimony: Acquiring Knowledge from Others’ in Alvin Goldman and Dennis Whitcomb (eds.), Social Epistemology: An Anthology, Oxford: Oxford University Press. 71-91.

Nozick, Robert, (2008) ‘Knowledge and Skepticism’ in Sosa, E., Kim, J., Fantl, J., and McGrath. M. Epistemology : An Anthology 2nd edition 2008. Carlton: Blackwell. 255-277.

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