is that really a fallacy?
is that really a fallacy?

On a recent podcast, I made a comment that most things that could be considered a fallacy could also not be fallacious. There are some that argue these things are always fallacious. This post hopes to explore a number of common fallacies and see if they are always fallacies, and also when folks might erroneously shout fallacy.

Remember, a fallacy is essentially just an error in reasoning, it does not make the conclusion wrong, but the process to get to the conclusion shows some form of error. In the same way, someone might have sound reasoning, but the conclusion could still be wrong too.

Appeal To Authority

appeal to authority

An argument from authority, also called an appeal to authority, or argumentum ad verecundiam, is a form of defeasible argument in which the opinion of an authority on a topic is used as evidence to support an argument.

What this is basically saying is you are appealing to an authority figure who’s opinion backs yours and basing your argument purely on this.

When is an Appeal to Authority not fallacious

  • Academic citations are used in every field
  • When something has been fully peer-reviewed*
    *please note the peer review process is not fully flawless, consider Andrew Wakefields ‘Study’ where he took a payout from lawyers.
  • When you can cite a number of experts in the field you are discussing and their papers etc (often which contain other citations)

It also depends on context, for example, if someone makes a claim that “X is the ONLY definition of Y” and you can provide academic and/or dictionary resources to show a number of different ways it can be defined, you are not committing an appeal to authority. You are not being prescriptive saying, “No it is defined as C and that is correct, your definition is wrong!” You are literally pointing out this word is defined in other ways.

This happened most recently when I was trying to correct someone that their definition of atheism and agnosticism was not the ONLY definition. I cited SEP, and even a few of my own blog posts which detail the different ways atheism and agnosticism are defined, and also explained the logic of the epistemological answers to the proposition.

I was called out for “appealing to authority” and then ironically was linked by the same person to the “American Atheists” who claim atheism is “only a lack of belief”.

I don’t really care about how you define things, but saying your definition is the only one, or being prescriptive with its use and saying everyone should use it bothers me.

I demonstrated that atheism as “a lack of belief” was not the only definition and I demonstrated that “without knowledge” was not the only definition of agnosticism. They don’t have to agree with the other definitions, but the fact is, they are there.

Rather than address what my point was they decided to project fallacies. Unfortunately, this is the dogmatic state of ‘New Atheism’ today that makes me embarrassed to call myself an atheist.

Consider this, if appealing to academic resources is fallacious, science is fucked.

When an Appeal to Authority is fallacious

  • When you cite an expert for something they are not an expert in.
    For example:
    A priest might be an expert theologian, but on matters of science, they should not be consulted.
    Dawkins is an expert in biology, no doubt, but it would be fallacious to cite him on matters of philosophy.
    To that end, any atheist telling you their “lack belief” definition is the ‘Only’ definition should not be cited either…
  • When you appeal to something just because it agrees with you, without much thought past that.
  • When you appeal to something that has been clearly refuted with evidence, e.g. all the evidence against the age of the earth.. but “ken ham says”

Slippery Slope

slippery slope

This is a logical fallacy in which a party asserts that a relatively small first step leads to a chain of related events culminating in some significant effect.

When is a slippery slope not a fallacy?

  • When the slippery slope is true, or at least the most likely outcome.
    e.g. If I let my kids choose what they eat, they will likely choose sweets and junk food, this will potentially lead to weight gain, obesity, and maybe even rotten teeth.

    The point here is, there are things that are genuine slippery slopes. If we can back up our claims with some form of evidence we can say that this is the most likely thing to happen but also be aware it might not.

    With the example above, most kids would probably choose sweets and junk food over eating a nice balanced diet, but not all of them.
  • When you’re trying to think of all possible outcomes and assess the likelihood.

    It is common for many of us to explore all potential outcomes, and any number of these could seem like a slippery slope. However, thinking of these slopes and considering the likelihood of them is not a fallacy.

When is a slippery slope a fallacy

  • When there is no basis or logical reason to assume that will happen.
    “If we let gays get married then we will eventually be letting people marry kids, dogs, horses etc”
  • When you’re basically “what iffing” and imagining the worst chain of events possible, and asserting this will be the case.


Straw Man

The Straw Man or Strawman is an informal fallacy based on giving the impression of refuting an opponent’s argument, while actually refuting an argument that was not presented by that opponent.

The strawman is one of those that can never actually be justified as not a fallacy, however they are sometimes not correctly called out.

When is a Strawman not a Strawman?

  • When you are providing a comparison to an argument so they can examine it through a different lens.

    For example, if you were to say ‘Expecting a normative academic definition to be updated based colloquial definition is the same as expecting a scientist to update the definition of evolution to “a change in kind” or that theory is “just an idea”.’

    You’re not asserting this as their argument, you’re literally showing them a situation where they would not accept it.
    Essentially, they are guilty of special pleading if they feel their colloquial definition overrides the normative one, yet don’t allow the creationist the same courtesy.
  • When you are questioning someone’s argument because it seems incomplete or incoherent and they can’t answer so you narrow your field of questioning to specifics (closed questions) instead of open questions.

    “When you say x, do you mean y?”

    Unfortunately, most people are not particularly great at communicating. On the internet, it is even harder because you don’t have the same levels of tonality or know the people well enough to make accurate inferences. Also many are not conversing in their mother-tongue so might not be describing their position in a way that makes sense, at least to you.

    Questioning what they mean, is not strawmanning them, it is literally trying to understand their argument so you can consider it properly.

Reductio Ad Absurdum

Reductio ad absurdum, also known as argumentum ad absurdum, apagogical arguments, negation introduction or the appeal to extremes, is a form of argument that attempts to establish a claim by showing that the opposite scenario would lead to absurdity or contradiction.

In short, it is when you take someone’s argument to a complete absurd extreme that it is essentially indefensible.

When is a Reductio Ad Absurdum not a fallacy?

  • When you are doing a comparative argument with something already a little absurd
    For example, Someone that equates non-theist to be atheist you could say “by that logic all non-boats are cars, or all vehicles are cars, but we don’t do that because there are key differences just as there are key differences in types of non-theist”
  • When you’re showing someone’s argument is incoherent and/or absurd
    For example, If someone rejects the normative use of words, whilst being prescriptive with their definition of a word, and also saying the definition of words is completely subjective, you can then define Science as the study of making pancakes and say we don’t need science any more because we already know how to make pancakes of different kinds from scratch and from a ready mix.
    If they then say you are wrong for your use of the word, they are guilty of special pleading.

When is a Reductio Ad Absurdum a Fallacy?

  • When you go to ridiculous extremes and essentially strawman.
    For example, if someone says something along the lines of, “If we all gave a little money to charity then the charities would have enough money to fund x.” and the response is “if we gave all our money to a charity we would be broke.” or “If we donate to a charity they will just use it for scientific experiments and not for funding x”
  • When you give an absurd example of why the argument is not the case.
    “The earth cannot be flat otherwise things would fall off the edge.”
    There’s plenty of evidence the earth is not flat, but this line of thought is fallacious.
  • Slippery Slopes
    Yeah, I mentioned them above, but essentially a slippery slope can also be an Ad Absurdum. Consider “allowing gays to marry will lead to people marrying kids, dogs, horses etc”. Not only is it a slippery slope, but it is also absurd to equivocate the marriage of loving consenting adults with paedophilia and beastiality.

Argumentum Ad Populum

Argumentum ad populum is a fallacious argument that concludes that a proposition must be true because many or most people believe it.

Essentially you’re equating the proposition to be true just because others believe it.

When is an Argumentum Ad Populm not a fallacy?

  • When it is genuinely the case.
    “Christians believe Christ is the son of God and our saviour”
    This is one of the key points of being a Christian. It’s part of the doctrine and part of the definition. You’re not asserting the belief itself is true, just one of the foundational beliefs of that particular tribe.
  • When used in conjunction with logical argument and evidence.
    “98% of scientists agree and the evidence indicates x to be the case, here is multiple studies that have been peer-reviewed”.

When is an Argumentum Ad Populm a fallacy?

  • When you are holding something to be true just because of the number of people who believe in it.
    “There are over 2.3 billion Christians, so it must be the true religion”
    “There are circa 5 billion non-Christians, so Christianity must be a false religion”
    “Other atheists say atheism is only defined as a lack of belief, so it must be”
  • When you are ignoring someone’s comments based on the number of people who say differently.
    for example when, “Actually, atheism is polysemous, as is agnosticism, your definition of them is just one of many” gets responded to with something like, “Other atheists say it is only a lack belief”

    The key point here is they are not only ignoring the fact that you are saying there are other definitions (rather than discussing which ones you prefer, or how they are defined), but they are digging their heels in. It’s almost like they are saying there can only be one correct definition of a word, and that definition is based on a popularity contest. The additional irony is they are choosing a colloquial definition over a normative one.

The Black Swan

The black-swan (or Ludic) fallacy is an inductive fallacy that states that if something has not occurred within the speaker’s experience, it cannot occur.

The funny thing about the Black Swan, its not really a fallacy, its just saying “just because this has happened the last 1000 times, doesn’t mean it will happen again” – e.g. it is saying be aware that induction alone might not be enough to determine truth.

Falsification is built on induction. Things are repeatedly tested in different ways that would disprove the theory, and all the while it is “not false” it is considered true.

It has become commonplace to see religious sites start touting the “black swan fallacy” as a way to discredit science. Atheists have now started to use the “black swan fallacy”.

However we can see there are times where it is a fallacious line of thought, as well as times when it isn’t

When is the Black Swan not a fallacious line of thought?

  • When it is a fact
    It is a fact that over an extended period of time without energy exchange, nutrition (usually in the form of food), humans will die.

    We may one day evolve into a species that gets a different form of energy exchange or indeed not need one at all, but then we wouldn’t be homo sapiens anymore, even if we were descended from them.
  • When it is definitional
    We will never find water that is not H2O.
    We may one day find a liquid that is like H2O but it would still be a different liquid because water IS H2O
  • When it has properly been considered and qualified
    “I believe the bridge will not collapse as I go over it, I based this on all the cars going over it being ok, the fact I have gone over it before, the construction, the safety laws and checks, but I am also open to that I could be unlucky and it collapses as I go over it”

When is it fallacious?

  • When it has not been properly considered and qualified
    It has rained for the last 3 days so it will rain today.
    How do you know? Have you looked at the weather forecast? Are you in an area that usually rains every day?

The key point about the whole black swan, is that it is more commentary on induction. Inductive logic and reasoning are very useful but should not be the only things considered, and you should be open to seeing the proverbial black swam.

So are these things always fallacies?

I hope by now you have come to realise that these things are not always fallacies. If someone has a complete argument with a number of different factors and cites an academic source or two, that is not a fallacy.

Comments should not be looked at on a line by line bases, but the argument as a whole. Too many folks spend their time shouting “fallacy” instead of addressing the actual conversation, and many get it wrong too.

In time I intend to address some more of these fallacies, so stay tuned!

Want to read more on fallacies?