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Logical Fallacies: Proof by Assertion

Debate graphic: Illustration 47468791 © Marynabolsunova -

[Originally published as Logic Lessons: Proof by Assertion]

As usual, the more I examine logical fallacies, the more I see how people blend their fallacies into dreadful monstrosities. I have had many experiences where people will attack by asserting that their opponent has a bad or ulterior motive, so be careful of Proof by Assertion because it lends itself to reinforcing other fallacies.

“Proof by Assertion” (sometimes “Proof by Repeated Assertion”, a relative of Circular Reasoning) is one of my favorite fallacies because I encounter it so very often. In its simplest form, Proof by Assertion happens when someone declares a “fact” without offering supporting evidence:

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Tweet stating: Creationism= God did it. What's scientific about that?

This is similar to the mantra, “Evolution is science, creation is religion.”

Another reason that I like “Proof by Assertion” is that it is conveniently linked with other fallacies (quite often with Appeal to Motive):

  • He is stupid, and blocked me on Twitter because he can’t support his view (includes similarity to Argument from Silence)
  • Creationists are not scientists (includes Genetic Fallacy)
  • Creationists are liars (insipid attempt to manipulate by someone who is unable to distinguish between disagreement on the interpretation of facts, and evidence)
  • It’s too bad you can’t deal with reality (ad hominem, plus what I think of as, “My belief can beat up your belief”)
  • Republicans only care about helping the rich get richer (includes Appeal to Motive)
  • The Bible was written by an evil spirit (No, I am not making up that absurdity)
  • I know what you’re gonna say, and you’re wrong (Poisoning the Well is in this, I think)
  • Osama bin Laden was a harmless old man that never hurt anybody (Yes, I’ve seen that foolishness, too)
  • Anyone who understand evolution accepts it, or, nobody who understands evolution denies it (seems to have a bit of Appeal to Ridicule

Although I may have used this before, here is one of the most wicked assertions and dishonest ad hominem attacks that I have ever encountered, from Norman the Paranoid Troll:

"...he wishes death on all non-christians..." Highlighted web comment
Although in an admittedly heated discussion, this was exceptionally vicious and petty.

I have noticed that assertions are often linked to questioning (or maligning) someone’s motive. In addition, this fallacy is very manipulative, and often used to provoke emotions in an attempt to gain control of the situation; it can be a great red herring to distract you from your purpose in the discussion. They not only contain “facts” that exist only in the imagination or worldview of the user, but often contain value judgments.

There is a version that I call, “You can’t get there from here.”

It is based on a clash of worldviews, when evidence presented will require someone to shed their preconceptions and actually follow where the evidence leads. People have asserted that evolution is a fact, and then appealed to a kind of ad populum or Appeal to Authority with, “Scientists believe it.”

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For example, “Evolution itself is accepted by zoologists, not because it has been observed to occur or can be proved by logically coherent evidence, but because the only alternative – special creation – is clearly unthinkable.” People who think like this are unwilling to abandon evolution, with all of its flaws and intellectually dishonest baggage, because the Creator does not fit with their materialistic uniformitarian presuppositions. But they stand by their declarations and appeal to “scientists” despite the evidence to the contrary.

Opinion vs. Facts

Many times, I have seen opinions asserted as fact in matters of morality and philosophy. For example, someone who says that the atonement of man by God through Jesus Christ is “immoral” because they do not like it is asserting an opinion as a fact.

The basic Fallacy of Assertion is easy to spot. It becomes more confusing when it is a part of another fallacy. Asking for supporting evidence or references can show that you are not falling for it. However, be careful not to call a foul when someone is simply expressing an opinion and not attempting to present an argument.

You can avoid this mistake yourself by adding, “I believe”, “I think”, “It seems to me”, “In my opinion”, and so on.

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Written by Cowboy Bob Sorensen

Although raised in a United Methodist family where my father was a pastor, I was challenged in my high school years to examine why we believe the Bible and hold to our doctrines. Years later, I drifted from the faith but never fully abandoned it. After I recommitted my life to Jesus in 2010, I was led to establish Weblogs to discuss matters of doctrine, apologetics, and especially biblical creation science. This grew into the Piltdown Superman site. My primary goal is to help equip the church in defending the faith, especially the foundations in Genesis.

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