Can we evaluate claims reliably and with a high degree of consensus without empirical evidence?

Question

If we seek a methodology for evaluating claims that fosters a high degree of agreement among individuals, one common approach is to base evaluations on empirical evidence. According to Wikipedia:

Empirical evidence is evidence obtained through sense experience or experimental procedure. It is of central importance to the sciences and plays a role in various other fields, like epistemology and law.

My question is: Is this the only viable approach for achieving consensus when evaluating claims, or are there alternative methodologies—either those that do not rely on empirical evidence or that adopt a more flexible or nuanced interpretation of it—that could also lead to a high degree of agreement?

In other words, if a group of individuals is tasked with evaluating a claim with the aim of reaching similar conclusions that are hopefully accurate (since the goal is to agree on truths, not falsehoods), is the use of empirical evidence essential to achieving that, or are there alternative methods?

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Addendum - Definition of 'Empirical Evidence'

There have been a number of related questions asked about this on this site:

• The meaning of empirical evidence?
• Ought we only form beliefs based on sufficient empirical evidence?
• Can belief in reincarnation be justified using empirical evidence?

If I had to offer my own definition, I would probably start by first quoting two additional paragraphs from the Wikipedia article:

There is no general agreement on how the terms evidence and empirical are to be defined. Often different fields work with quite different conceptions. In epistemology, evidence is what justifies beliefs or what determines whether holding a certain belief is rational. This is only possible if the evidence is possessed by the person, which has prompted various epistemologists to conceive evidence as private mental states like experiences or other beliefs. In philosophy of science, on the other hand, evidence is understood as that which confirms or disconfirms scientific hypotheses and arbitrates between competing theories. For this role, evidence must be public and uncontroversial, like observable physical objects or events and unlike private mental states, so that evidence may foster scientific consensus. The term empirical comes from Greek ἐμπειρία empeiría, i.e. 'experience'. In this context, it is usually understood as what is observable, in contrast to unobservable or theoretical objects. It is generally accepted that unaided perception constitutes observation, but it is disputed to what extent objects accessible only to aided perception, like bacteria seen through a microscope or positrons detected in a cloud chamber, should be regarded as observable.

Empirical evidence is essential to a posteriori knowledge or empirical knowledge, knowledge whose justification or falsification depends on experience or experiment. A priori knowledge, on the other hand, is seen either as innate or as justified by rational intuition and therefore as not dependent on empirical evidence. Rationalism fully accepts that there is knowledge a priori, which is either outright rejected by empiricism or accepted only in a restricted way as knowledge of relations between our concepts but not as pertaining to the external world.

I would also quote parts of this article on empirical philosophy:

Empirical philosophy prioritizes knowledge derived from sensory experiences and systematic observations. t asserts that all knowledge originates from sense experience and rejects innate ideas. Key figures include Aristotle, Francis Bacon, John Locke, George Berkeley, and David Hume. Empirical philosophy greatly influences the scientific method and evidence-based practices. Criticisms include neglecting reason and intuition and struggling to explain abstract concepts and a priori knowledge.

Empirical philosophy is a cornerstone of epistemological inquiry, emphasising the primacy of sensory experience and observational evidence in the acquisition of knowledge. This philosophical stance contends that all understanding arises from our interactions with the external world, challenging the notion of innate ideas. Historical figures such as Aristotle, John Locke, and David Hume have greatly contributed to its development, positioning empiricism in stark contrast to rationalism. Yet, what are the implications of relying solely on empirical methods, and how does this approach navigate the complexities of human cognition? The exploration of these questions illuminates the enduring relevance of empirical philosophy.

Finally, my attempt at defining empirical evidence would be something like this:

• It consists of "stuff" that exists objectively "out there" (thus, I am assuming from the outset that views like idealism and solipsism are false). This "stuff" can be directly perceived through one's senses or indirectly with the aid of technology that enhances sensory capabilities.

• It should be possible for others to observe or experience this same "stuff" if they follow the same protocol under similar conditions. This could range from simply watching something with the naked eye to performing a complex sequence of steps to replicate an experimental result.

• Mathematical proofs might arguably be classified as a special case of the above. They can be experienced through our senses after following a sequence of logical steps (the steps of the proof). For instance, it's akin to empirically verifying that a particular strategy leads to checkmate in chess. One can verify this on a physical chessboard with real pieces or a virtual chessboard displayed on a computer screen—both of which are physical and perceptible.

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Addendum - What do I exactly mean by 'claim'?

By claim I mean statements that assert that something is true in reality / real life / the real world / the set of all things that are real. For example, claims of existence (X exists), which can range from very mundane things to very extraordinary things, such as:

• dogs exists
• Donald Trump exists
• black holes exist
• aliens exist
• Bigfoot exists
• ghosts/spirits/souls exist
• psychic powers exist
• God exists
• etc.

We could also extend this (and make things more complicated) by considering claims that include a temporal dimension (i.e., claims about the past or claims about the future):

• Hitler existed
• The Big Bang occurred
• It will rain in New York tomorrow
• Etc.

Answer 1

Broadly speaking, no. But it depends on how strictly you define "empirical evidence".

We could say that empirical evidence is the best/only reliable means of coming to truth. But like most statements, there is a lot one could unpack there, if one wishes to be precise. I would caution against trying to draw a strict categorical distinction between empirical evidence and not that, and judging things to be reliable or unreliable purely based on that. The line often isn't that clear, and there is also unreliable empirical evidence.

Hallucinations are a thing (and people have a hard time differentiating religious experiences from those). But this doesn't mean we should throw out eyesight as evidence altogether, because it's unreliable (I mean, it is after all one of our primary means of observing the world). Rather, we should recognise that it's not perfectly reliable, and we should figure out when it is more reliable and when it's less reliable, and take measures to make it more reliable (e.g. double checking something or corroborating it with other evidence).

Testimony?

Personal testimony is mostly just empirical evidence with extra steps (steps which make it a whole lot less reliable).

The person giving testimony (hopefully) has empirical evidence of the event. You have empirical evidence of them giving testimony (although we probably wouldn't call this empirical evidence of the event itself).

And you can evaluate the reliability of testimony to determine how likely what they're saying is to be true, much like you can evaluate the reliability of eyesight to determine whether what you're seeing is actually there. We've done that for eyesight, and found it's generally accurate, but sometimes people also hallucinate and often they misremember what they've seen. We've also done that for testimony, and... it's really much worse than people intuitively think and that society thought for a long time. Our legal system treated it as much more reliable than it actually is (up to the modern day, and will probably continue to do so), and that landed a lot of innocent people in prison. See, for example, the Innocence Project.

Expert consensus?

One might consider expert (specifically scientific) consensus to be a special case of testimony. This doesn't just rely on someone's recollection of what they saw one time. Instead, this generally involves carefully controlled and carefully monitored experimentation and record-keeping, there are often multiple experiments, and the results are reviewed by others, and it can be independently verified by them. Scientific journals maintain certain standards that increases the reliability of what they publish.

This is also something we can evaluate the reliability of. The consensus of scientists tends to be reliable (although that statement is unfortunately becoming a lot more controversial in the modern day). The consensus of psychic "experts" most likely isn't in any way reliable (although they are good at making vague statements and reading people to trick them into thinking they're making highly accurate statements thanks to some supernatural ability).

Maths, logic, etc?

You mentioned maths already, but I'll just note that for completeness' sake.

We certainly have plenty of reliable tools for evaluating evidence and for drawing inferences from that. One could debate whether such things, in themselves, could be included as an extension of empirical evidence, but this is mostly semantics.

Although some of this is a lot less reliable than it is typically presented as. Logic, for example, is a very useful tool. But there are undeniably a lot of people drawing contradictory conclusions from that. Specifically in relation to god claims, at least (which often involve rather abstract arguments that are divorced from reality and unlike the arguments we use in other context, which might go a long way to showing where logic becomes unreliable).

Is reliability subjective?

Reliability can be defined as number of accurate evaluations / number of total claims evaluated. Although it's also useful to consider true and false separately.

That can be objectively evaluated for some set of claims (just plug in the numbers), if you can agree on whether those are true or false (which almost all people do about most things - there are just a few claims where people throw all of this out the window, because... reasons).

So no, it's not hugely subjective (even if there is some subjectivity in different ways to measure it, and ways to select claims to evaluate, but that evaluation in itself can be evaluated).

Consensus?

I'd consider consensus to be a distinct issue from reliability.

A method can be reliable regardless of how many people agree that it is reliable or how many use it.

A lot of people don't seem to consider reliability to be one of the most important factors in epistemology. If you're looking for consensus, you'd first have to get people to agree that it is one of the most important factors, if not the single most important factor, or the only factor that really matters.

Now, if people follow the same method, one might expect that if the method is reliable, that most of those people would agree on a conclusion. This could be another dimension of reliability. Agreement doesn't tell you that a claim is true, but disagreement does provide an upper limit on reliability. If only 50% of people agree, then it's impossible for the method to be more than 50% reliable, regardless of which conclusion is true.

Answer 2

^{This answers an earlier version of the question.}

Claims that make no assertions or predictions about the world can be assessed without resort to empirical evidence.

For example, claims about what conclusions follow from mathematical axioms can be evaluated based on logical proofs, without resort to empirical evidence.

Answer 3

Yes. We can rely on testimony in the place of empirical verification.

According to Robert Audi and his epistemological schema, we can rely on others who have verified empirical claims for us. This form of knowledge is called testimony. Testimony is arguably used more frequently as a source of knowledge than direct empirical verification given our short life spans, and the immensity of the world of potential truths around us. In fact, almost all of our formal education, even in the natural sciences, is based on testimony of one form or another. The testimony of our teachers, the testimony of researchers, the testimony of science reports, etc.

Answer 4

I assume you mean: „Can we evaluate claims about the empirical world reliably and with a high degree of consensus without empirical evidence?“

Note. Without this addition the answer is “yes” for claims in mathematics as @Lowri has rightly pointed out.

• At best we can refute a claim about the empirical world without employing empirical evidence if the claim is inconsistent, e.g., contradictory in itself or contradictoty to reliable claims.

• In addition, we may dismiss a claim about the empirical world without employing empirical evidence if the claim is presented without any argument.

• But the standard method to refute a claim about the empirical world is to show that the conseqences of the claim contradict reliable observations, hence referring to empirical evidence.

Answer 5

Yes, it happens all the time.

However, the likelihood of achieving consensus depends entirely on the nature of the claim, and the characteristics of the group or audience you are making the claim to.

For example, if you make a claim that you and your friend saw a squirrel run across your path in the forest you would have a good chance of convincing almost anyone because we have empirical evidence that squirrels exist, even if we cannot objectively prove the presence of one at the time and place you claim you saw it.

If you were to make a claim that Bigfoot crossed your path you would have a harder time convincing most people, but if you were to make this same claim at a cryptozoology convention you would find a more receptive audience, and therefore a better chance at achieving a consensus of those who believe your claim.

Personal testimony does carry some weight in evaluating any claim, but reliability is ultimately subjective.

And then there is circumstantial evidence... It may be physical, but as you have defined it in the context of your question it may not be "reproducible" by following any specific methodology in a way that makes it relevant to the claim. However, the evidence may be fitted neatly into a model of reality to make a claim.

Consider a DA putting together a case: The weight of the evidence fitting a specific narrative of events that explains the crime may be sufficient for the jury to reach a consensus if there is no plausible counter narrative that fits the evidence whereby the defendant is innocent.

Answer 6

Yes. For every series of observations, there are an infinite number of theories that match the observations or whatever experiment you perform. In order to pick one of them over another, you must rely on other scientific principles that have nothing to do with observation, such as the parsimony of a theory.

“Predictive power” and similar epistemic virtues still cannot tell you which theory to believe or get a consensus on, since again, one can invent an infinite number of theories that match predictions.

Empirical evidence does help you rule out certain theories though as Popper pointed out. For example, the hypothesis that all swans are white are trivially ruled out by observing a black swan. Note that contrary to some other answers here, testimony is still a form of empirical evidence. Since the testimony itself acts as an observation of the world from your end, and the person giving the testimony presumably observed something if his testimony is reliable.