Kritical Kwikies 03 Affirming the Consequent



welcome to my ongoing series on critical thinking this time I'd like to highlight a particular logical fallacy that's very popular with a certain YouTube personality let's talk about affirming the consequent what does that mean what does it tell us if someone commits this fallacy how can we tell if someone has made this mistake can we fix this mistake and what can still be learned if we do fix it first what is affirming the consequent it goes like this premise 1 if a then B premise to B is true conclusion therefore a must be true this is a fallacy that means faulty logic just because b is true that does not necessarily indicate that a is true let's illustrate this with my mystery jam again if this Jam were made of raspberries it would be red this Jam is red does that mean the Jam is raspberry no this could still be strawberry strawberries are red too let's hear an example of this from Nathan Oakley if the earth is a sphere number 1 that's a begging the question policy then we will experience weight changes as we move from the equator that's if P the earth is a sphere then we will experience weight changes Q we do experience weight changes Q therefore the earth is a sphere B that would be an affirming the consequent formal logical fallacy I pulled that clip from and his video on this is worth a watch I'll link it below let's break this down premise 1 if the earth is a sphere then we will experience weight changes as we move from the equator premise 2 we do experience weight changes conclusion therefore the earth is a sphere as Nathan Oakley explained this is a perfect example of affirming the consequent we'll just ignore that begging the question stuff for now but hold on a minute isn't this the basis for pretty much all of science in science class they taught us how you make your hypothesis and then you test the hypothesis to see if it's true is all of science based on a logical fallacy if that's what you're thinking you're really close but as they say the devil is in the details Nathan made the same mistake but no that's not quite the scientific method here's the actual scientific method let's see if you can spot the difference premise 1 if a then B premise 2 B is not true conclusion a is not true see the difference they're putting in that knot eliminates the logical fallacy let's see that in action with our mystery Jam premise 1 if the jam is made of pineapple it will be yellow premise 2 the jam is red not yellow conclusion the Jim is not pineapple now that we see how this works let's go back and fix that thing about the weight changes premise 1 if the earth is a rotating sphere then we will experience weight changes as we move from the equator premise 2 we do experience weight changes in exactly this way conclusion therefore the earth could be a sphere there no fallacy see how easy that was to fix clearly nothing to get worked up over this particular observation doesn't prove the earth as a sphere all it does is fail to disprove it we'll hear more about proofs in a later video for now I want to ponder for a moment what might have happened if Nathan had corrected Bob instead of shouting him down this observation was unable to rule out the globe but are there any models this observation could disprove Nathan Oakley likes to shout and rant whenever he thinks somebody has made a mistake like this it's unfortunate because it brings the discussion to a complete halt I wonder is Nathan blocking the conversation on purpose could he be worried somebody might fix this logic and turn it around to disprove something that's important to him the weight changes by latitude are consistent with the globe but they don't prove the globe if the earth is flat then certainly one of these tests will be able to disprove the sphere so far not this one we'll have to keep looking thinking is critical because sense is not common

3 thoughts on “Kritical Kwikies 03 Affirming the Consequent”

  1. Great video. Since hypothesis' are if/then statements then yes, Nathan is stopping the conversation by saying they are all logical fallacies then assuming that this is a victory for the flat earth. What Nathan should do is show the exact reason this is a logical fallacy then he should offer a counter explanation which shows why this supports the flat earth. Of course he doesn't have enough understanding of either the globe or flat earth models to do this and actually even calls models "reification fallacies" by saying that we don't live on a model although no one is claiming that we do.

    Let's be honest, Nathan uses this tactic so often that it is actual a 'fallacy fallacy'. The irony is Nathan claim that air pressure is the "antecedent" for a supposed container around our atmosphere.

  2. I'm sorry but premise 2 and conclusion @ 2:50 is the same as :
    If NOT B then NOT A,
    Or if B is false A is also false…
    Which is not a correct conclusion. As Nathan likes to point out, if I eat a lot of burgers I feel full. I'm full therefore I ate a lot of burgers. Except it's not true, I had Chinese food for dinner… 😉

  3. Wonderfully put. I wish you'd gone into the synthetic-analytic distinction in epistemology to nail down why methodological naturalism uses the system of falsification and evidential corroboration. The philosophy underpinning science is not generally well understood by the layman.

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