Logic and Writing (Part One): Deductive vs. Inductive Reasoning and valid vs. sound arguments

December 6, 2017

HypothyroidWriter.com logic in writing part one blog post Sarah Lentz
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Logic in Writing: Part One

Deductive vs. Inductive Reasoning

Those who know me best won't be surprised to read that I prefer deductive reasoning to inductive. I've never been a fan of making general statements about a group of people, based on a few specific examples. 

This is how we get statements like "you get what you pay for" and "anyone who voted for him/her is my enemy / an idiot / going to he**."

We can do better.

This series of posts has to do with the relationship between logic and writing -- or the relationship they ought to have.

Nothing prevents a writer from exhibiting one logical fallacy after another -- or a particular favorite over and over again -- but if we want our writing to be clear, true, and persuasive, it pays to learn what logic can teach us. 

There's plenty of writing out there that pays little if any homage to the importance of building not only a valid but a sound (cogent) argument. 

This series is one blogger's attempt to fight back and help other writers to strengthen their writing -- and become better thinkers in the process.

"I have good reason to believe ..." 

Not all inductive reasoning consists of making assumptions about groups of people who do X, say Y, or wear Z. 

If you've ever made a decision because you had "good reason to believe _____," you've used inductive reasoning. You're basing your belief on a specific example or set of examples that make you think your conclusion is likely to be true.

It's something we all do -- at least some of the time, if not as a habit. 

If you've ever made a hypothesis and set out to disprove it, you're using inductive reasoning. You have good reason to believe something, but you don't know for certain that it's true -- so you do what you can to put it to the test. 

But sometimes, maybe, you just adopt that hypothesis as "likely to be true."

Maybe you go one step further and treat it more or less as something "most people with any sense" would agree is true. 

And that's where we get into trouble. That's when we stop thinking and let our assumptions do the work for us. 

That's when anyone who disagrees with that something that "most people with any sense would agree to be true" becomes someone who must, therefore, not have any sense. 

This is where we end up with an argument that looks perfectly valid but isn't sound. It isn't sound, because the premises are still unproven. They're assumed to be true -- but not proven to be so.

They're conclusions drawn from inductive reasoning, elevated by popular consensus to the status of "fact." 

But they remain unproven assumptions. And any conclusion drawn from them -- even if it logically follows from them -- cannot be sound. It's no more "true" than the assumptions or opinions that led to it. 

But for many people, it's true enough. And anyone who disagrees must not be worth listening to, because their words deviate from the popular consensus. If "most people with sense" agree with an assumption, then anyone who disagrees with or challenges it must not have any sense. So, why listen to him? And why put that assumption to the test?

Familiar? It should be. 

This has become the way most people argue. They won't take seriously any challenge to their precious assumptions, because they've already decided that anyone who disagrees with those assumptions is not someone whose words have any value. 

They must be not only wrong but laughably so.

For example, ask anyone who takes evolution for granted what he thinks of creationism. Or ask someone who believes everything negative the media say about a particular candidate what she thinks of those who voted for him or her. 

Arguments that are valid but not sound

For an example of an argument that is logically valid but not sound, we can take the argument suggested by many who vilify those who voted for a candidate whom they hold in contempt:

Premise 1: I’ve read some terrible things about that candidate (C1), and I see no reason not to believe the reports. That candidate must, therefore, be evil.
Premise 2a: Only an evil or morally bankrupt or willfully ignorant person would vote for an evil candidate (like C1), or
Premise 2b: A person would have to be evil or morally bankrupt or willfully ignorant to vote for an evil candidate (like C1).
Conclusion: Anyone who voted for C1 must be evil, morally bankrupt, or willfully ignorant.

Premise 1 is based on hearsay (second-hand information sources -- possibly unreliable) and the conclusion drawn from that. 

The options for premise 2 are both assumptions, in that they fail to take into account the possibility that those who voted for C1 might have had other motives -- such as a firm belief that, of the two options who stood a real chance of winning, C1 was the lesser of two evils.

As a deductive argument, though it’s valid -- since the conclusion logically follows from the premises -- it fails the cogency test. It’s not a sound argument, because the premises are not proven to be true. They’re based on either hearsay or assumptions regarding the motives of those who voted for C1. 

One point that needs to be made is that voters can disagree on which candidate was truly the lesser of two evils -- without becoming enemies. It is possible to be civil and even charitable toward those with whom we disagree.

But voters who rejected C1 -- and often, by extension, those who voted for him/her -- may have done so from a sincere belief that “only an evil or morally bankrupt or willfully ignorant person would vote for C1, and I can’t be friends with such a person. She doesn't even deserve civility, let alone my forgiveness!”

Only if they consider the possibility that the voter’s motives were other than evil or morally ambiguous can they be open to seeing those who voted for C1 as people who might have been every bit as disgusted (possibly for good reason) with the other candidate (C2) as they are with C1.

In other words, both may be voting from a place of moral conviction. 

And one voter may give the other the benefit of the doubt, respect her decision, and move on, while the other may persist in holding the person who voted for C1 (or C2) in contempt. 

Reconciliation may yet be possible (if not imminent). 

But head space comes at a premium; we're not obligated to accommodate the petty insults of those who assume they know our motives and character better than we do.

From a different angle . . . 

If we want to argue from inference (using inductive logic), we can say the following:

Premise 1: I’ve heard and read terrible things about this candidate (C1), and I see no reason not to believe them. C1 must be an evil person.
Premise 2: Voter A voted for C1, because he refuses to believe the reports about him; therefore, he’s willfully ignorant (or delusional) and his vote for C1 stems from that.
Premise 3: Voter B voted for C1, because she’s morally bankrupt and sees nothing wrong with what C1 reportedly did, since she likes some of C1's policies and wants him or her to be president. Therefore, Voter B’s vote for C1 stems from her moral ambiguity.
Premise 4: Voter C voted for C1, because he’s the kind of person who gropes women and treats them like postage stamps. Therefore, Voter C’s vote for C1 stems from his moral depravity.
Conclusion: Those who voted for C1 did so because they are willfully ignorant (or delusional), morally ambiguous, or evil.

Premise 1 is still based on hearsay, a refusal to question that information, and the conclusion drawn from it 

It's an argument in miniature:

     Premise 1a: I've heard terrible things about this candidate (C1).

     Premise 1b: I believe these reports to be true (I have "good reason to believe" they're true.)

     Premise 1c: Only an evil person could be guilty of the things C1 is reportedly guilty of. 

     Premise 1-conclusion: Therefore, C1 must be an evil person.

On the face of it, premises 2 through 4 certainly make the conclusion more likely, which is what we’re going for when we argue inductively. Premise 2, though, makes an assumption about Voter A that may not be true. Voter A may have good reason to question the reports about C1 and to doubt their truthfulness. 

In any case, we go from specifics (voters A, B & C -- who voted for C1) to generalities: the conclusion that pertains to “(all) those who voted for C1.” 

But is the conclusion true -- in every case? No. Because it doesn't (and can't) verify the motives of every single person who voted for C1 and prove that those motives stem from moral depravity, moral ambiguity, or willful ignorance. 

Can it be true that some who voted for C1 were morally depraved, morally ambiguous, or willfully ignorant. Sure.

It can likewise be true that some who voted for C2 were morally depraved, morally ambiguous, or willfully ignorant. 

It can also be true that some who voted for C1 and some who voted for C2 did so because they honestly believed their candidate was better for the country than the other candidate -- even if they didn't entirely trust the candidate for whom they voted (they trusted the other candidate even less).

Some people on either side of the issue will make assumptions about (all) those on the side opposite from theirs. We don't have to. It's easier than thinking about all the possible reasons why someone might have voted for the candidate we dislike, but if relationships matter more to us than being right, it makes sense to at least try to see the situation from the other person's point of view. 

Resting on assumptions is passive -- not active. It's the easy way out, as long as you don't mind being written off as someone who's incapable of (or averse to) considering any viewpoint that differs from her own. 

What I believe about either of the candidates is based on what I have good reason to believe, because I have limited knowledge of the true characters of both leading candidates. While some voters knew more about one candidate or both, I suspect most of them knew about as much as I did -- which isn't enough to make an infallible assessment of anyone's character, especially given the questionable reliability of second-hand information.

It's just enough to make an educated guess as to which candidate would be better than the other, based on what we consider the most important criteria.

Reason and Relationships

Not everyone will understand or even try to understand why you voted the way you did -- or why you did something else that angered them. 

Their inability (or disinclination) to think past their assumptions doesn't obligate you to explain yourself repeatedly in a futile attempt to help them understand. 

If, for some reason, they'd rather continue to see you a certain way -- as someone morally or intellectually beneath them and deserving only of their perpetual blame and petty insults -- the best you can do is minimize their access to you. And pray for them (not easy, I know!).

You don't have to trust them, and you don't have to want to be around them. Just do that one thing for them, because their souls still matter. And we all need someone to pray for us.

And be careful that you don't fall into the same trap of holding a grudge against those who are convinced you need (but will never have) their forgiveness for what they see as a betrayal.

It's all too easy to get your thoughts mucked up with resentment -- to the point that, even if they offered an olive branch, you'd rather see them strangled with it. 

And that poison can easily be passed on to our kids. It doesn't have to, though.

We're all weak. Some are just more aware of it (thanks to frequent reminders). 

Faith and Reason

I can't end this post without some mention of how this all relates to faith. 

If I'm using premises that I take on faith and coming to a conclusion based on those premises, which are tenets of the Catholic faith but are rejected by many who don't profess the Catholic faith (and even by some who do), my conclusion may be 100% valid, and --  according to Catholic dogma -- completely sound. 

Yet many will reject it because they reject the premises. And what do I offer in defense of my argument and its premises, if those who challenge it are not Catholic or have no respect for those dogmas? 

I would have to know far more than I do about how those dogmas became part of the Deposit of Faith, because only then would I know if I could draw on something other than the writings of the Church Fathers and Doctors -- all of which would likely be rejected as authoritative sources by those who reject Catholic dogmas. 

[And even if I have supportive quotes from the Bible, many -- including some Catholics -- will choose to interpret them differently. I write this not to disparage non-Catholic Christians (who share my belief in many of the same truths) but to make a point.]

Yet there are many who reject Catholic teaching who will heap insults on us for questioning statements upon which they rely for their conclusions -- but which they cannot prove -- and who have nothing but blind faith in their sources to back them up. 

So, while they ridicule us for depending on our Faith to support our arguments, they build an argument of a similar structure but with weaker materials and a shifting foundation, and then curse every storm that comes to challenge it.

In closing

Part Two of the Logic in Writing series deals with logical fallacies that are, essentially, distractions from the essence of the argument. It won't be the very next blog post, but it's coming. 

Your turn. 

Is there something else you'd like to add that might interest other readers of this post? 

Thank you for spending some of your valuable time, here, and I hope to read something from you, too! 

Logic in Writing: Do you use deductive reasoning most of the time -- or inductive? And when is an argument valid but unsound (not cogent)? #amwriting

By Sarah Lentz

Writing and designing book covers are two of Sarah Lentz's favorite things. She lives in Minnesota with her husband, their four kids, and two messy but adorable guinea pigs.

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