Logical Fallacy Question Time - Mostly Science

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Logical Fallacy Question Time


Recently a reader asked us the below question-


“I would like to know what fallacy this is: It cannot be proven that there are not other life forms living in the caves of Mars, therefore I cannot believe that there is no life on Mars.”


This is known as the “Argument from Ignorance” (in Latin: argumentum ad ignorantiam) or “Appeal to Ignorance” and is a type of informal logical fallacy. I actually listed this as one of the most common logical fallacies in my opinion in a previous article. I will go into a little more detail here and also share some other examples that others and I have come across. But first we can break down the example you provided.


In this case the arguer proposes that we cannot prove life does not exist on Mars, and so they cannot fathom a Mars without life forms. Now there are ways that scientists can look for life off-world as shown here and here. So clearly we do have methods for looking for both complex and intelligent life, as well as simple life beyond Earth and therefore this disproves any potential notion that we cannot look for life elsewhere. Perhaps the arguer is asserting that until we bring proof or life or lack of life on Mars, he/she will continue to believe that there is. The problem with this is that you would believe something without any credible evidence and by putting yourself in this position you have instantly made yourself ignorant on the topic.

Now let me make a few things very clear. Just because this person is committing a logical fallacy does not make them necessarily wrong (this is the fallacy fallacy), however the problem is with your reasoning and therefore the methods used to come to your conclusions are fallacious and not to be trusted. You may turn out to be right and NASA could come to us tomorrow and demonstrate proof. However, before you celebrate being “right” you have still argued your opinion from ignorance, rather than putting forward a hypothesis with evidence to back it up.

If you are comfortable in doing this, then fallacious thinking may well pervade itself into many areas of your life beyond your interest in astrobiology. I would not celebrate being right on chance. Additionally by this very same logic, I could argue for magic dragons since you have not proven to me there are no magic dragons. Furthermore, this style of fallacious reasoning aims to shift the burden of proof. Put simply, the burden of proof states that, in an argument, the person putting forward an assertion must show evidence for said assertion.


A brilliant philosopher by the same of Bertrand Russell (the astute looking fellow shown atop this article) came up with a still popular example of the argument from ignorance, known as “Russell’s teapot”. Russell wrote:


If I were to suggest that between the Earth and Mars there is a china teapot revolving about the sun in an elliptical orbit, nobody would be able to disprove my assertion provided I were careful to add that the teapot is too small to be revealed even by our most powerful telescopes.

But if I were to go on to say that, since my assertion cannot be disproved, it is an intolerable presumption on the part of human reason to doubt it, I should rightly be thought to be talking nonsense.

If, however, the existence of such a teapot were affirmed in ancient books, taught as the sacred truth every Sunday, and instilled into the minds of children at school, hesitation to believe in its existence would become a mark of eccentricity and entitle the doubter to the attentions of the psychiatrist in an enlightened age or of the Inquisitor in an earlier time.”


You can probably see what Russell was being cheeky about.

An example that I recall personally during a conversation was when this person made the argument that there is so much we don’t know about this world and that therefore ghosts could exist. Again, this is fallacious reasoning and arguing from ignorance. If there is no proof whatsoever, then it doesn’t make sense to believe purely on blind faith and it makes even less sense to adjust your life according to these falsely reasoned beliefs. As for a potential counter argument of “well I do these rituals and have these beliefs just to be safe”, please refer to Pascal’s wager.


An example I have seen others come across is with respect to the magical, snake-oil peddlin’, magic hocus-pocus, quackery woo-fest that is homeopathy (as you can tell I am not fond of this pseudoscience). Arguing that because people claim homeopathy works (placebo mixed with fraud) and because there is so much we don’t know about quantum physics and how things work (despite all the evidence against homeopathy) that surely homeopathy does work somehow is purely fallacious reasoning and a great example of an argument from ignorance. In fact, people claiming that “more research needs to be done” seem to neglect two simple facts; firstly that medical research does not have an infinite magic sack of money to be able to fund everything (look at Australia where 55% of health and medical research projects were deemed fundable, but due to budget constraints, only 19% could be funded). Secondly, there comes a point where “more research” becomes unethical, as you are essentially doing things like entering patients into trials where we already know the answers to the questions. Ultimately you end up funding magic (which I wrote about here).


Anyway that should sum things up for you in plenty of detail. However, if you want to know more about arguments from ignorance, then the Wikipedia page is a good start, Rational Wiki has a very brief page under their logic section and more about the great Bertrand Russell can be found here, at the Stanford Encyclopaedia of philosophy. Finally, thanks for your question!

Dr. Christopher Haggarty-Weir

Vaccines, Immunology, Infectious Disease, Drug Discovery/Design, Molecular Biology, Business and Philosophy.

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