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Fundamentals: Abductive Arguments

In this video, Geoff Pynn follows up on his introduction to critical thinking by exploring how abductive arguments give us reason to believe their conclusions. Good abductive arguments don't guarantee their conclusions, but give us very good reasons to believe their conclusions. This sort of inference is called "inference to the best explanation."

Speaker: Dr. Geoff Pynn, Assistant Professor, Northern Illinois University.

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  • winston default style avatar for user Dylan
    What's the difference between an abductive argument and an ampliative argument?
    (30 votes)
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    • ohnoes default style avatar for user Tejas
      An abductive argument is a form of an ampliative argument. It is not the only type of ampliative argument, though. Ampliative arguments are any arguments that increase the level of confidence that we have in the conclusion. Abuductive arguments are more specific, in that they are trying to find an explanation for certain observations that you make.
      (27 votes)
  • leaf yellow style avatar for user Bright Sol
    Why can't human logic always work?
    (5 votes)
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    • leaf red style avatar for user Velvetia
      I'll tell you the answer in a story!

      In a classroom, there were students and professor who had one philosophy and one only:
      If he could not see, hear, touch, taste, or smell, it didn't exist.
      One student decided to test his theory.
      Student: Does cold exist?
      Professor: Of course it does! You're just wasting my time.
      Student: No, it is the absence of heat. What about darkness?
      Professor: Yes, it does! -about to turn his back on the student-
      Student: No, it's the absence of light. We call it darkness, but really it's just the absence of light. Look, do you have a brain?
      Professor: I DO!
      Student: Well, can you see, hear, touch, taste or smell your brain?
      Professor: No.
      Student: Therefore, according to your theory, you do not have a brain.

      To put it simply, humans make mistakes and cannot always be right.
      (Good question! ^.^)
      (24 votes)
  • hopper jumping style avatar for user Lucas De Oliveira
    If there is an abductive argument, then there is an adductive argument. How works it?
    (5 votes)
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  • blobby green style avatar for user chadi.r.aoun
    What is the difference between abductive, ampliative and inductive arguments?
    (4 votes)
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  • leaf blue style avatar for user David Harbour
    Are conclusions based on our experience abductive arguments?
    (3 votes)
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  • blobby green style avatar for user 3blueskies
    Hi! Are there any books that have practice problems/passages for critical thinking?
    (3 votes)
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  • leafers seedling style avatar for user Britt
    I've often wondered about the 'simple explanation' criterion mentioned at
    The idea that a more simple explanation is a better explanation sounds nice, and I also recognize this idea from Occam's razor, but I've also wondered: what if the simple explanation isn't the right explanation? I would say that we should try to find the truth, both in critical thinking and arguments, as well as in science. An argument might be simple, but it might not be true, even if it does explain the evidence perfectly.
    So, what I'm really trying to say: shouldn't truth or correctness be more important than simplicity? Or is it implied that we can never really know 'the truth' (if there is such a thing as an objective truth), and that we therefore might as well chose the easiest explanation?
    (3 votes)
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  • orange juice squid orange style avatar for user karen
    I'm taking a critical thinking class and in my class, we describe arguments that are set up in this way as inductive. Are abductive and inductive arguments the same thing?
    (3 votes)
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  • starky ultimate style avatar for user Ian Goh
    Is an abductive argument the same as an inductive argument?
    (3 votes)
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  • aqualine ultimate style avatar for user TAsha Deberry
    Why can't an argument be true or false?
    (1 vote)
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    • piceratops ultimate style avatar for user trek
      Statements can be true or false.
      Arguments are made of statements.
      Arguments are valid or invalid based on whether the conclusion is entailed by the antecedent.
      An argument can be completely valid even if all of the statements are false.

      All boys like to punch other people.
      Mother Theresa was a boy.
      Therefore Mother Theresa liked to punch other people.

      Every statement there is false, but the argument is logically valid.
      (5 votes)

Video transcript

(intro music) Hi! I'm Geoff Pynn, and I teach philosophy in Northern Illinois University. In this video, I'm going to talk about abductive arguments. Abductive arguments rest on an inference to the best explanation . The simplest way of thinking about this idea is in terms of "why"-questions. Suppose you tell your friend that someone has a crush on him, and his cheeks turn bright red. Why did that happen? What's the explanation? Well, the most natural answer seems to be that it's because he was embarrassed to find out about the crush. That's why his cheeks turned red. This example can be turned into an abductive argument. The premise is "Charlie's cheeks turned red "after I told him that Lucy had a crush on him." And the conclusion is "So, Charlie was embarrassed to learn about Lucy's crush." Notice that the promise doesn't guarantee that the conclusion is true. Something else might explain it instead. Maybe Charlie was eating a jalapeno, and his cheeks turned red because it was so spicy. Or maybe he just got scratched by a cat, and he's having an allergic reaction. If you let your imagination rip, you'll be able to think of other possible answers to the question "Why did Charlie's cheeks turn red?" too. Nonetheless, given your background knowledge, C seems like it's the best explanation for P, or at least it's a contender. If it is, then P gives you good reason to believe C. That's how abductive arguments work. We know that some stuff is true (these are the premises), and reason from that to whatever is the best answer to the question "Why are these things true?" Our knowledge doesn't guarantee that the explanation is correct, but that's OK, because abductive arguments aren't supposed to be deductively valid. Abductive arguments are nonetheless extremely common in all walks of life. It's a very important critical thinking skill to be able to make, spot, and evaluate abductive arguments. Think of how a TV detective solves a crime. Suppose she knows that the murder weapon was found in Smith's trunk, Smith doesn't have an alibi, Smith had a motive and Smith failed the lie detector test. The best explanation for all this evidence is that Smith's the murder. And so the detective believes that Smith is the murder, and for good reason. She passes this argument on to the prosecutor, who uses it to convince the jury to believe its conclusion too. Abduction also plays a crucial role in science. Scientific hypotheses often rest on inferences to the best explanation for some observed data. For example, that's how the planet Neptune was discovered. In the early 1800s, astronomers noticed small discrepancies between the observed orbit of Uranus and the predictions that Newton's theory of motion made about what the orbit should be. the best explanation for these discrepancies was that they were caused by another planet that no one had ever observed. And it turned out that this was correct. There was another planet, which we know as Neptune today. So what makes something a good explanation? Well, there's a lot of debate about this amongst philosophers, but here are two characteristics of good explanations that most generally agree about. First, the more an explanation fits in with everything we already know, the better it tends to be. Consider another possible explanation for the discrepancies between the observed orbit of Uranus and the predictions of Newton's theory: that Newton's theory was wrong. To accept that Newton's theory was wrong would require giving up on lots and lots of other very good explanations, and so wouldn't fit very well with what astronomers already knew. The idea that an unobserved planet was causing the discrepancies fit much better with what they already knew, and so counted as a better explanation. Second, other things being equal, a simpler explanation is better than a complicated one. Here's another possible explanation for Charlie's blush: Maybe he misheard you, and thought you said that Penny had a crush on him, and so he's embarrassed to learn about Penny's crush, not Lucy's. This explanation could be right, but its needlessly complicated. Since the original explanation is simpler, it's preferable to this more complex one. Both fit and simplicity come in degrees, and other factors are also relevant to how good an explanation is. There's no sure-fire recipe for saying when an explanation is the best one. One way to challenge an abductive argument is to try to come up with a better explanation of the data than what the argument provides. Another way to challenge an abductive argument is to look for more evidence to add to the promises. Suppose the detective also found out that Smith had a very clever nemesis who had a motive to commit the murder and had been planning to frame Smith for a long time. Then Smith's being guilty would no longer clearly be the best explanation for all of the detective's evidence. Now there's another, perhaps equally good, contender, namely, that Smith was framed by his nemesis It's important when relying on an abductive argument to make sure that you get all of the evidence that you can and then consider all of the evidence before drawing your conclusion. That's because the fact that a conclusion is a good explanation for some evidence doesn't mean that it's a good explanation for all of your evidence. So, summing up. Abductive arguments are a kind of ampliative argument: their premises don't guarantee their conclusions. Abductive arguments involve an inference to the best explanation: their conclusions are supposed to be the best explanations for their premises. Abductive arguments play a central role in everyday life and scientific inquiry. Good explanations tend to fit with our background knowledge and to be simpler than the alternatives. And finally, you can challenge an abductive argument by coming up with a better explanation for the premises, or by finding additional relevant evidence that isn't well-explained by the conclusion. Subtitles by the Amara.org community