Reductionism and the problem of testimonial belief

For 10 weeks in term 3 I completed an online course on “Theory of Knowledge” from the University of Oxford’s department for continuing education. As part of this course, I have to submit two assignments. The second, was due at the end of the course and is copied below. The first can be read here.

What is the reductionist position as regards the epistemology of testimonial belief? Is such a view defensible, do you think?

In this essay, we will examine the nature of knowledge and the relationship of testimonial belief to it. We will look at the problem of testimony and the various ways of responding to this problem before addressing the question above.

A summary of the structure of knowledge

Some context is necessary here. I assume that justification, truth and belief are all necessary conditions for knowledge but in and of themselves are not sufficient conditions for an agent to claim knowledge. In addition, we need an understanding of the nature and type of the justification given. Normally we would require justification to be rational and based on evidence. In order to maximise true beliefs we are concerned with epistemic rationality: rational thinking and ways of thought that lead to the acquisition of a maximum number of these true beliefs. Epistemic rationality is either internal or external. If it is internal, the agent is aware of how they formed their beliefs and can justify them. If external, the agent may not be aware of how they formed these beliefs and is therefore not in a position to justify them consciously. However, if these beliefs were formed through epistemic norms, ways of acting and thinking that likely lead to the formation of true belief, we can still claim them as justified (Pritchard, 2014). This distinction is important when we consider testimonial knowledge and I will provide some examples later in the essay.

Testimonial knowledge

Testimonial knowledge is the knowledge gained by the transmission of information verbally, through reading or other activities where an agent is gaining knowledge from another agent. We depend on testimony for forming many of our beliefs. Most of what we claim to know through formal education is acquired through testimony. The knowledge that our parents impart to us is also testimonial. Testimony is therefore central to knowledge and can be a way of acquiring knowledge (I acquired true belief X through testimony) and also a way of justifying the knowledge an agent claims (Belief X is true because I was told or I read it). For example, I justify my belief that the moon orbits planet earth because I was told this in school. I also received this knowledge through the testimony of my teacher at the time.

The problem of testimony and the responses to it.

The problem with testimonial knowledge arises from our inability to independently justify knowledge that we gain through testimony. By independently verify, I mean that we cannot verify this knowledge in most cases without resorting to some other form of testimony. For example I know that the moon orbits the earth because I was told this by my teacher but if I wish to independently verify this, I normally would have to consult a textbook (a form of testimony). To illustrate this further, I could look for other means of justification: I could call NASA to ask them to verify this is the case but this would also mean I was relying on their testimony. Without actually acquiring a telescope and making empirical observations of the movements of the sun, moon and stars and making advanced calculations I would have no way of independently verifying this knowledge without resorting to more justification via testimony.

Reductionism and credulism both try to answer this problem. Reductionism claims that testimony based beliefs will always ultimately reside on non-testimonial evidence. Or, if we are to rightly hold a testimony based belief then we must also hold evidence that is not testimony based (Pritchard, 2014). This is an epistemically rational internalist position because reductionism requires an agent to know how they formed those beliefs and be able to explain how they formed those beliefs.

The reductionist position easily applies for local beliefs, things we can verify through our own perception and perhaps through our own empirical investigations, like a preschooler learning about the world through perception and empirical experience, for example, I know what a banana tastes like from experiencing it. Reductionism gets harder to apply with non-local beliefs, where we are simply unable to empirically verify a testimonial belief, for example, my belief that the moon is not made of cheese.

Credulism offers another response to the problem of testimonial knowledge. This position holds that we don’t always need independent grounds to justify a testimony based belief (Pritchard, 2014). Instead, it claims, such beliefs are justifiably held unless there is special reasons to doubt them. This is an example of external epistemic rationality where we don’t require an agent to be able to justify how they formed their beliefs so long as they have been following epistemic norms. In this case, an epistemic norm could be that being told something by an authoritative source is one way to maximise true belief. Holding to views acquired by testimony in this way is an entirely rational thing to do.

When credulism is modified thus we can begin to appreciate its advantages. For example, most of the knowledge that we learn at school and university is taught to us by teachers or experts in a particular field. Many of the things that we may wish to independently verify, we cannot. Would we say that something we learned in school or university was not knowledge? Intuitively not. We may regard facts acquired in this way as more robust than picking something up in a pub from a casual conversation. So we can have a methodology in terms of discriminating how reliable someone might be by their level of expertise.

The problem with credulism is that it can seem to make a virtue out of not knowing but of trusting (Pritchard, 2014). Perhaps we should be more sceptical of the information that we receive, after all, teachers can often make mistakes, or be misinformed themselves (I know from my experience of being one!)

Is reductionism defensible?

We can think of both reductionism and credulism as lying on a spectrum of justification. On one hand we have the reductionist who requires that every belief acquired through testimony needs to be independently verified and on the other hand we have the credulist who accepts that so long as these testimonial beliefs have been acquired through epistemic norms then there is no need for independent verification.

The reductionist position is the ideal because it forces agents to acquire more than one line of evidence to justify a true belief. Ideally agents should be able to justify those beliefs acquired through testimony via other means, be it through perception or empirical investigation but this ideal has some serious difficulties.

Firstly the process of independent verification of every belief acquired through testimony would take an extremely long time, enough to render the exercise impractical on an individual level. If an individual was responsible for independently verifying each one of their beliefs acquired through testimony, they would not be able to necessarily maximise their true beliefs. If we try to answer this by allowing many agents to independently verify different beliefs they hold in common, we run into the problem of relying on testimony from other agents again. Thus this doesn’t seem to be an epistemically rational way to maximise true belief.

The second problem that arises from the reductionists position in that it is not always possible to independently verify beliefs gained via testimony. Should we discount these beliefs as knowledge then? It seems that if we were to ignore any beliefs that we were not able to independently verify we would miss out a large number of true beliefs and would therefore be impoverished in what we know.

The third problem is in some cases it is not necessarily appropriate to independently verify our testimonial beliefs: “it is improper to place too many intellectual demands on people’s everyday beliefs. … if the reduction is possible, requiring it is overly demanding; the requirement to reduce hyper-intellectualizes testimonial justification. Young children, for instance, lack the intellectual capacity to consider complicated issues regarding the reliability of their parents or others who give them testimonially-based beliefs, and so it is improper to place epistemic demands on them.” (IEP, 2018)

Therefore whilst reductionism offers a seemingly strong answer to the problem of testimonial knowledge, it leaves us with the more problems regarding maximising our true beliefs.

Credulism too has problems associated with it. How do we know that another agent isn’t trying to decieve us? One proxy I sometime hear people use for knowing if a written argument is well founded is that the argument contains references. This shorthand is often used in informal academic online discussions within education but what if one agent is deceitful and simply puts many references so that readers will trust them?

In reality, most of our beliefs will be justified through testimony. We should strive like the reductionist to independently verify these beliefs where possible. Where we can’t we should accept those beliefs where we can be more confident of the source of the testimonial belief. In this way, our beliefs will dot across a spectrum, where each individual belief occupies a position between pure reductionism and pure credulism.


IEP (2018) accessed on 26th July 2018\

Pritchard, D. (2014) What is this thing called knowledge? 3rd edition. Routledge.

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