May 23 2019

How Do We Know?

A Reddit thread in the Skeptic subreddit is framed as criticism toward skeptical philosophy. The questions it raises are all important, and honestly the poster should have just framed his points as questions rather than criticisms, because they reflect not problems with skeptical philosophy but their poor understanding of it. So the first lesson here is – humility. Don’t assume that an entire field you don’t fully understand is wrong. Rather, start with the assumption that you have more to learn, and then let proponents make their best case.

There are many good responses in the thread, which shows that a reasonable understanding of skeptical philosophy is out there in the community. The questions are very common beginner errors, and so they are worth responding to in detail. My first response, however, (as others in the thread have pointed out) is to begin with a basic text of the subject. Read a philosophy book. I humbly suggest The Skeptics’ Guide to the Universe, which is designed to be a primer on skeptical philosophy and directly addresses all of the poster’s questions. But there are many good books out there, and even basic philosophical books on epistemology will do (they don’t have to be explicitly skeptical).

I point this out because I frequently encounter people who are trying to do philosophy without even realizing it, or without an appreciation for the depth of philosophy as an intellectual field. Philosophy is one of those things that everyone thinks they can do, even without a lick of education on the topic. Inevitably they make basic mistakes, often ones that were dealt with thousands of years ago by the first philosophers. This would be no different than making pronouncements about a highly technical field of science without ever having studied it, and without really knowing the position of experts.

He begins:

‘Fact’ – What is a ‘fact’? Google search says: “a thing that is known or proved to be true”. Here is my problem: ‘known’…by whom? I am from India and have seen both villages and towns. Different things are ‘known’ in different communities. For example, people in rural areas ‘know’ there exists witches and ghosts.

This is a basic question of epistemology – how do we know anything, and what does it mean to know something? Here is also a pearl – don’t rely on essentially a dictionary definition for insight into a technical term or concept.

In a way we don’t really know anything and facts are all relative. There are very few absolutes when it comes to human knowledge. Such basic “facts” are referred to as first principles – what are the ideas that we can agree must be true or that we can assume are true, and then use those as a starting point for subsequent exploration of reality.

Science itself is not a set of “facts” but a method of exploration. It starts from specific premises, and it doesn’t even hold that these premises are Truth, just that they are necessary for science to function. We call these premises methodological naturalism – every material effect has a material cause, and there is no magic or miracles (arbitrary suspensions of the laws of nature). At least you cannot invoke such miracles when making an argument. Based on this premise, science uses logic and observation not to prove things correct, but to prove things wrong. (That is a key point – you can never prove something wrong if you can invoke miracles as needed.) By conducting experiments and making observations science can exclude hypotheses that are incompatible with the evidence. Whatever is left, the explanations that have survived dedicated attempts at proving them wrong, are then considered tentatively to be possible or even probable explanations. The longer a scientific notion survives, and the more independent lines of evidence that lead us to the same conclusion, the higher our confidence in that idea.

It’s an endless process. We build models that are capable not only of explanation but of prediction, and then we test those models, modifying and rejecting them as necessary.

Throughout his comments the poster seems to be relying on a false dichotomy, that skeptics believe something is either a known fact or should be ridiculed. This is not how skepticism works at all. Rather, we advocate for using a valid set of philosophical and scientific methods, and we criticize those who rely instead on invalid methods (poor logic and pseudoscience). It’s all about method, not belief.

His next point:

Whatever the case maybe, there are many things we don’t know. Obviously, filling those gaps with ‘God/Satan/demon/etc did it’ is laziness, but if those phenomena already have supernatural explanations believed by people, it doesn’t necessarily become false.

This is a straw man. Skeptical philosophy does not treat something as false simply because people believe in it for the wrong reasons (that is the fallacy fallacy). Skeptics must acknowledge ignorance. What we criticize is the argument from ignorance – making a claim based on the lack of knowledge. We can’t explain mental phenomena to an arbitrary degree of confidence, therefore belief in spirits is justified.

On a related point:

Russell’s teapot argument – yes, it was a good argument. Sure, I cannot prove or disprove the existence of a teapot floating between Mars and Jupiter. But there are many things like that which are true but have no evidence – what you ate, say, 100 days ago, your thoughts, your consciousness, your feelings, etc.

Again, this is a straw man based on the poster’s own ignorance of philosophy. The philosophical position is not that Russell’s teapot does not exist, but simply that it is unjustified to claim that it does based solely on our inability to prove that it doesn’t. That’s it.

Also the poster draws the wrong lesson from the premise that there are things which are true but for which we cannot have evidence. Sure, no serious philosopher doubts that. The position of scientific skepticism towards such claims is not that they must be false, but agnosticism. Science is agnostic toward anything that cannot be explored through objective evidence. Such things are simply unknown (unless they contain a logical self-contradiction). And again, what we criticize is claiming to know something is true that is not amenable to evidence or falsification.

We also consider plausibility of any claim, and apply logical principles like Occam’s razor to determine the relative probability of competing hypotheses. It’s not about proof – it’s science is all about probability.

If you claimed that you ate a grilled cheese sandwich 100 days ago, I would have no reason to doubt or challenge that. I simply don’t care, I am technically agnostic toward the claim, but it is so trivial as to not be worth exploring. If, however, what you ate 100 days ago was somehow a critical piece of evidence in a murder trial, then we would need to see some evidence. Show me a picture, a receipt from a restaurant, or produce some unbiased eye-witnesses. Otherwise, you cannot admit the claim as evidence. It doesn’t make the claim false, just unknown.


Richard Dawkins’ “Religions are contradictory/’which God’ argument” – that doesn’t mean they are all wrong. Disproving ‘phlogiston theory’ didn’t mean Science was wrong. If one religion is wrong, that doesn’t mean all religions are necessarily wrong. This will be an abuse of using induction.

But that is not the argument. The argument, rather, is that because religions generally contradict each other in their claims (at multiple levels from big picture to small details), they cannot all be true. In fact, if any one of them is completely true, than all other religions are false to whatever extent they contradict the one true religion. The argument is that anyone who believes in one faith, rejects all other faiths. They are atheists or agnostics towards every religion save one. So atheists reject faith in only one more religion than believers – a statistically small difference.

This is an important realization, and is meant to pierce the cultural bubble that many religious believers seem to live in. It is helpful to fully understand that the world is full of people who believe their religions as vehemently as you believe yours, they have the same confidence and similar reasons for thinking they have the one true faith. And yet, you reject their faith. In fact you reject hundreds of faiths, and countless faith-based claims. So how can you blame atheists for rejecting yours? By some estimates there are 4,200 religions in the world. If you believe one of them, then you reject 4,199, while atheists reject 4,200. Not a big difference from that perspective.

These are fun questions to explore, and why I find philosophy fascinating. To emphasize my primary recommendation – go into philosophical questions with humility, and also the principle of charity. Assume you are ignorant and try to learn what philosophers are actually saying. They have been deeply debating these questions for thousands of years, so it is unlikely you will find a fatal flaw in their arguments by casually shooting from the hip.

When I point that out, and that criticisms are often based on a misunderstanding of what scientific skepticism actually says, often the rejoinder is that they have heard “skeptics” make those bad arguments. Fair enough – then criticize those specific self-identified skeptics. Just don’t confuse their errors with scientific skepticism itself. This is where the principle of charity comes in. Try to understand what the best arguments are on one side.

In fact the entire post would have been fine if the poster framed it as – I have heard some people who call themselves skeptics make these arguments, which I think are not valid. What does the community say? Rather than criticizing skeptical philosophy itself based on a misunderstanding gleaned from random individuals.


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