Logical Fallacies: Omission and Ambiguity

Logical fallacies are errors in reasoning that can invalidate an otherwise good discussion, formal argument, or debate.

The fallacies discussed here have to do with misdirection or misinformation. Fallacies of Omission occur when important or even necessary information is left out of an argument. Fallacies of Ambiguity create confusion by using unclear or poorly defined words or phrases in order to misdirect the argument from the evidence supporting the other side.

This is the final part in a series of episodes on logical fallacies. Already we have discussed Fallacies of Relevance and Component Fallacies. There are a lot of logical fallacies out there, enough to have entire college classes on them. These episodes only covered a few of the more common ones in each category.

This concludes the series on logical fallacies. At first glance these appear overwhelming and overly academic. However as you learn them you will start to see people using them. This will help you to better understand the reasons for certain decisions or how management has been influenced to keep using a deprecated technology that hasn’t been supported in years. Study them, re-listen to the series if need, so that you will not only be able to recognize when you or others are using them but also know how to defend against fallacious arguments.

Episode Breakdown

Fallacies of Omission

Fallacies of Omission are logical errors where necessary information is omitted. It often results in the argument being directed away from the missing information.

Argumentum Ad Ignorantium

Literally translated it means “Argument from Ignorance” or it can be called the Appeal to a Lack of Evidence. This is the idea that because the other person cannot disprove a premise or idea that it must be true. You will run into the lack of evidence fallacy a lot when trying to get older managers or leads to try newer technology, they will come up with something that the newer tech was never designed to do or that there is no information about. The tricky part of overcoming this fallacy is that the burden of proof lies with the person making the claim so if they something isn’t possible the burden is on them to prove it, not on you. This is why scientific research uses a null hypothesis (opposite of what they are trying to prove) because the lack of evidence doesn’t disprove their hypothesis it only fails to disprove the null hypothesis.

Argumentum Ad Speculum

Also known as Hypothesis Contrary to Fact, this fallacy tries to proves something in reality using examples from a fantasy or made up world. The idea is that hypothetically if A happened, then B would be the result of it. The problem is that all of the examples and evidence supporting the argument are hypothetical, or based on accepting a hypothetical premise. This is the other side of the “What if this happens” of the previous fallacy, instead you’ll see this happen after the fact, “Well if we’d changed platforms back when I suggested we wouldn’t have these problems”. While fun to play time-travel/butterfly effect mental games, these hypotheses are typically irrelevant and do not actually provide evidence for or against an argument in the real world. To overcome this you have to politely point out that talking about what could be doesn’t solve the problem a hand, also you don’t know what issues you would have faced had a different decision been made.

Stacking the Deck

The name comes from cheating in card games where a person will place cards in the deck while shuffling to benefit them in the game. In this fallacy, the person making the argument ignores evidence or examples that disagree or disprove their conclusion and only provide evidence in support of their case. The ‘No True Scotsman’ Fallacy is a specific type of Stacking The Deck that defines something so narrowly that it excludes obvious examples then says that those examples to the contrary are not “truly” a part of what is being defined because they don’t meet the narrow definition. You’ll see the ‘No True Scotsman’ variant of this fallacy often when neckbeards get to arguing over who is the most hard core, ex: Real software engineers don’t need IDE, they write it all in command line VIM. Similar to the hasty generalizations, this fallacy is more nefarious as it is used when the deception is deliberate not accidental. This is an insidious fallacy as no matter how much evidence to the opposite you present they will just say that it doesn’t count. There’s not much more to do here than walk away at this point.

Loaded Question

Also called the “Complex Question”, the question in question is worded in such a way as to imply something that has not been logically proven nor assumed or accepted as a premise. While a joke, the “What have you been fighting this week?” at the beginning of the show is a loaded question as it assumes that Will has been fighting something. Similar to begging the question, or leading questions, this is something that is seen in television shows especially when mocking lawyers or when showing an unscrupulous lawyer. Another fallacy you’ll see from older developers when trying to get them to move to newer technology, they think they are being clever when asking these questions especially in front of non technical management. This is one of the most frustrating fallacies to address, you have to point out that they are making assumptions in the question that are not valid given the current information. This may mean calling them out for misleading the conversation so should be done tactfully.

Argument from the Negative

Similar to Argumentum Ad Ignorantium, sometimes they can be used interchangeably. This fallacy occurs when someone assumes something is true just because the opposite is false. Unless you are dealing with binary options, just because you are able to disprove the argument of your opponent does not mean that yours is true. You’ll run across this when debugging with a team where you run a test, some tests are ‘rule in’ meaning if positive they say this is most likely the problem whereas others are ‘rule out’ so if they are positive it says this is most likely not the problem. What happens is when someone runs a ‘rule in’ test and thinks that because it wasn’t ruled in that it can’t be the problem (the result of a ‘rule out’ test). Understanding simple boolean algebra shows the error because A NAND B = !A OR !B; or in english the opposite of nothing is something, not everything.

Fallacies of Ambiguity

Ambiguity occurs when people use homonyms with similar meanings or even entire phrases that could take on multiple meanings in an argument. These changes in the meaning of what is being said can cause an argument to be fallacious.

Fallacy of Composition

An error with inductive reasoning, this fallacy comes about from implying that the properties of the parts are the same as that of the whole of an argument or object. It’s an over generalization similar to the Hasty Generalization fallacy, except it focuses on part of added together rather than lack of evidence. You’ll see this when dealing with QA or consuming an API, this part of the code or this endpoint is slow or buggy therefore the whole thing is going to be slow or buggy. While an individual part of the code or a specific call may be slower than expected that does not mean that the overall codebase or API is slow, it doesn’t ask if the code base is taking that slowness into consideration. Getting past this type of fallacy involves asking a lot of questions about other parts of the argument or the whole to show that it is not the same as some of the parts.

Fallacy of Division

The opposite of the fallacy of composition, division is an error with deductive reasoning. This fallacy states that what is true of the whole is also true of the individual parts of that whole. It also could be applied to aspects or properties of that whole and falsely claim they are also true of the individual parts. While some people choose their workplace based on it’s corporate mission or views, not everyone who works at a place is concerned with their activism or philanthropy. Division also involves asking questions, this time about more evidence that the individual part is also like the whole. That it is part of the whole is not enough.

Fallacy of Equivocation

Equivocation is the act of deliberately changing the meaning of a word or phrase in the middle of an argument. The term comes from the root words “equal” and “voice” referring to the concept that a single word can mean two different things. When done in a comedic fashion this might be called a play on words, however what makes it a fallacy is the deceptive nature of it’s use to trick or mislead someone in an argument. This happens all the time in political rhetoric, one side will misrepresent what the other person said or take it to an illogical conclusion based on a different interpretation of the words used. To address this fallacy you must establish a definition for the words you use, though even doing so may not always work as it tends to be done when the originator is not around.

Fallacy of Amphiboly

Amphiboly comes from the same Greek roots as the word “indeterminate” and is similar to equivocation. Instead of the definition of words being ambiguous, the confusion or deception comes from the structure of the grammar so that one interpretation may be correct and another one incorrect. This is analogous to the ambiguity of certain programming language parse trees and Will’s frustration with languages that count white space in the syntax. It comes about when words have more than one use within a sentence such as being a verb and an adjective or adverb. The phrase “waste paper” could refer to “toilet paper”, left over clippings from a craft project, or an environmental infraction. Overcoming the amphibian phrasing is the same as with equivocation, you have to get a clear definition of what is being said.

Fallacy of Reification

The mathematician Alfred Whitehead called it the “Fallacy of Misplaced Concreteness” as it involves treating an abstraction as if it were a concrete object. This fallacy treats a word or phrase as if it were the actual idea that it represents. When used in literature this would be called a “figure of speech” or “metaphor” and used to help understand an abstract concept by using concrete terms around it. Rampant in HR and marketing propaganda, you’ll see this a lot when a company is trying to “rally the troops” or get everyone on board with something they are doing or changing. You have to call it for what it is in this fallacy, if you are dealing with an abstraction point out that the person is acting as if the they are dealing in the absolute when they are talking about abstract concepts.

Tricks of the Trade

Just because it’s a logical fallacy, doesn’t mean that it has to be pointed out right now. Sometimes, you need to deal with the emotion behind something before dealing with the thing.

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