Circuits
Now that we know how good arguments are put together, how do we account for ones that don’t measure up?
Let’s think about our circuit again. What happens if it’s missing the battery? Or the switch? Or the wires? Well, the lightbulb won’t turn on.
Arguments are the same way. If we are missing the Minor or Major Premises, or if the connection between them is missing, the Claim doesn’t “turn on”, i.e. the claim isn’t valid.
What is a Flaw?
A flaw in deductive reasoning occurs when there is a gap in the logic that leads from the premises to the conclusion. This gap means that even if all the premises are true, the conclusion may not necessarily follow.
The wording above is important. Let’s dig into some of that.
Gap: A gap in the logic can be hard to understand or find when looking at only the words on the page. But that is precisely why we draw a circuit. A gap in a picture is far easier to see.
...even if all the premises are true...: though we of course do not know if the premises given to us in argument are true, our job is not to question them. Our job is always to evaluate the argument, the structure.
the conclusion may not necessarily follow: this one is hard! A flaw does not prove that the claim is definitively wrong, only that we've now opened up the possibility that it may be.
What is an Assumption?
An assumption in deductive reasoning is an unstated premise or belief that, when taken for granted, leads the argument toward validity.
Assumptions and flaws are fraternal twins; they look different but come from the same place. If a flaw in deductive reasoning is the presence of a gap in the logic, an assumption is what fills that gap.
Put another way, they are the “affirmative” and “negative” sides of the same coin. If there is a gap in the argument, the author has assumed that a certain thing is true (assumption) and has overlooked the possibility it may not be (flaw).
The Unicorn Assumption
For those who have already been exposed to the concepts of Necessary and Sufficient Assumptions, don’t worry about that yet. We’ll get there. For now, we are going to refer to the assumption described above as the Unicorn Assumption.
We call it that because it is the perfect assumption to fill the gap, or rather the assumption that perfectly fills it.
A simple example for you: Lunch costs $5, and you can afford to pay for lunch. What have we assumed?
The Unicorn is that you have exactly $5. A perfect fit. There are all sorts of other things that we could have assumed that could be helpful in various ways, but we always start with the unicorn.
How do I find the flaws and assumptions?
Arrange every clause/sentence you have and determine the role of each.
Build a Circuit from it
Examine that circuit to find what is missing.
Verbalize and fill that gap(s), using both ASSUMES and OVERLOOKS.
That does sound simple, and that’s the point. We WANT it to be easy.
BIG NOTE:
Assumptions and Flaws can be found in three places in an argument circuit:
A missing Major Premise (Rule)- The classic. “You gave me all the facts, but I don’t know WHY that means the conclusion is true.”
A missing Minor Premise (Facts) - This is simply “You made a claim and told me the law, but I don’t know what actually HAPPENED to the subject of your claim, so…”
A missing LINK BETWEEN the Minor and Major Premises - This one is subtler. You’ve got facts, and you’ve got a rule that warrants the conclusion. But, they don’t overlap, the facts don’t TRIGGER the rule.
EXAMPLES
Putting Flaws into Circuits
Missing Major Premise
Mrs. Smith is a bad choice for mayor because she was not born in this city.
This argument certainly seems flawed. And, for those who have studied "classic" flaws in the past, you may even be able to notice right away that this is an Ad Hominem attack, one that focuses on details about the person instead of their qualifications.
But, that only helps us if we are asked about the flaw. What if we need to know about an assumption? Or how to strengthen this argument? We need to be far more precise about how we analyze so that we can have the most useful information possible.
So, let's start with finding the Claim. What is the intended message, the opinion of the author?
We always look for those adjectives and adverbs, descriptive words, as they often point us to opinions. In this case, "Mrs. Smith is a bad choice for mayor", or so says the author. So that's the opinion, and thus the claim.
We take it, split it into subject (Mrs. Smith) and predicate (is a bad choice for mayor) and put it at the top of our page.
That makes "she was not born in this this city" the Minor Premise, as that is direct evidence about our Subject, Mrs. Smith. Great, let's get that up there too.
That's everything we have, leaving a glaring hole in the place we SHOULD have our Major Premise, our rule that would tell us when we can know that someone is a bad choice for mayor. For now, I will simply put a blank, red-filled square in its place.
Now, we need to verbalize the flaw/assumption. Remember, we always start with "The author assumes that..." and aim to connect the dangling pieces. In this case, the author
assumes that not being born in a city makes you a bad choice to be its mayor.
The most common objection we hear is "Yes, of course, that's obvious, that's exactly what the author has already said." But take a closer look. The author is CLAIMING that the person is a bad choice based on the fact that she is not from the town, but do we KNOW that the claim is warranted based on that fact? Who said so? There needs to be that RULE in order to claim that it is true, and there is no such rule. It is as if you see bad behavior in someone and claim that there are guilty of a certain crime, but there is no law or statute or precedent DEFINING that crime. So how can you say that he's guilty of it??
In exactly that spirit, we must always also express the gap in the negative. So we simple take our phrase and negate it. The author
overlooks the possibility that not being born in a city MAY NOT make you a bad choice to be its mayor.
Either of those can now go in our red box, or even both!
Missing Minor Premise
Mrs. Smith is a bad choice for mayor because anyone born in another city is a bad choice for mayor.
This argument certainly also seems flawed, and perhaps more obviously so to you. We don't actually know anything about Mrs. Smith!
We start again with finding the Claim, which conveniently hasn't changed from the previous example.
That leaves us with "Anyone born in another city is a bad choice for mayor." This is a general rule that points to the predicate of our conclusion. So, it must be our Major Premise and thus should go on the right.
This time our glaring hole in the place we should have our MINOR Premise, our facts about Mrs. Smith, our subject. A blank, red-filled square does the trick!Now, we need to verbalize the flaw/assumption. The author
assumes that Mrs. Smith was born in another city
and
overlooks the possibility that Mrs. Smith MAY NOT have been born in another city
Put both in our red box and we're all set!
Missing Link
Since Mrs. Smith owns a house in another city, she is a bad choice for mayor. After all, if you’re not a city resident, you’re a bad choice to be mayor.
We're now in more opaque territory. There seems to be a good deal going on here. Let's unpack it.
Our claim hasn't changed:
Now we have two extra pieces of information, so it's a good thing we divided up our claim. Any facts about Mrs. Smith go on the left, and any rules we have that tell us when someone is a bad choice for mayor go on the right. We've got one of each, and it looks like this:
Notice that there is no arrow connecting the two premises. Why? Because owning a house in another city is not actually the same thing as not a city resident.
They're awfully close, but they aren't synonymous. We call this a
FALSE EQUIVALENCY.
You'll hear it called a lot of things from a lot of different resources. Don't get too fussed about terminology, call it what you want, but know that this is what we mean when we say it!
OK, back to the flaw...
In this case, the flaw/assumption is the **LINK**, the connection between the two terms of the false equivalency - the author
assumes that Mrs. Smith owning a house in another city MEANS that she is not a city resident
and
overlooks the possibility that Mrs. Smith owning a house in another city MAY NOT mean that she is not a city resident
Put both in our red box and we're all set!
Of course it’s not always as straightforward as this, but it is more often than most people give it credit for. Many arguments, even complex ones, can boil down to a missing Major or Minor Premise. As long as the corners of your central circuit are clear in your mind, you can find that flaw!