Logical Reasoning

PT148 · S3 · Q22 The return of organic wastes

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The return of organic wastes to the soil is a good solution to waste disposal problems only if the wastes are nontoxic and not too much energy is expended in transporting them.

Conclusion (Hence)

Returning organic wastes to the soil is a good way for small-scale organic farms to solve their waste disposal problems.

Evidence

Returning organic wastes to the soil is a good way to solve waste disposal problems only if the wastes are nontoxic and not too much energy is expended in transporting them.

For small-scale organic farms, the wastes are nontoxic and not too much energy is expended in transporting them.

Evaluate

Whenever we do Parallel Flaw, we prime our brains for the Top 5 famous flaws (Necessary vs. Sufficient / Part vs. Whole / Unproven vs. Proven False / Causal / Ad Hominem).

Whenever we do Flaw or Parallel Flaw and see any Conditional Logic in the argument, then we know there's like a 95% chance that we're being tested on Necessary vs. Sufficient, the flaw in which an author presents a conditional logic premise but then applies that conditional rule using some Illegal Reversal or Negation.

The first sentence of this argument gave us a conditional logic rule, signified by "only if", which always indicates the necessary idea that goes on the right side of the arrow:

Returning organic wastes Wastes are nontoxic to soil is good solution to → and waste disposal problems Low Trsnpt energy

We would then anticipate that the author will either say, (this is an illegal reversal, and this is what the argument does), or the author will say (this is an illegal negation).

The author establishes that for small farms, the two ideas on the right side are true, and then she illicitly concludes (by reading the rule backwards) that the left side must be true about small organic farms.

Goal

We just want something that provides a conditional logic premise and then argues via an illegal reversal, i.e.

Premise 1: X → Y Premise 2: For thing A, Y is true. Conclusion: For thing A, X is true.

22.

Which one of the following exhibits flawed reasoning most similar to the flawed reasoning exhibited by the argument above?

  1. Plants thrive if they get

    Bad Premise Match

    First we look for the conditional (if = left side) get an abundance of moist / light / nutrient → thrive From there, we know the argument has to give us another premise that says "Thing A is thriving" and then conclude "Thing A must be getting an abundance of moisture, light, and nutrients". But the 2nd premise does not say "Thing A is thriving". In fact "thriving" isn't even mentioned again in the argument.

    4% picked this

  2. When every country has equal

    Basically Valid

    First we look for the conditional (when = left side) every country has equal globalization will access to markets → give a way for each country to optimize From there, we know the argument has to give us another premise that says "the right side of this conditional is happening" and then conclude "the left side of this conditional is happening". Instead, the other premise is a fact that is saying, "in 20 years, the left side of the conditional will be happening". Thus, we could fairly conclude that "in 20 years, the right side of the conditional will be happening", and that's more or less what the conclusion here does do. In symbolic terms, we were looking for this: Premise 1: X → Y Premise 2: For thing A, Y is true. Conclusion: For thing A, X is true. We got this: Premise 1: X → Y Premise 2: In 20 yrs, X is true. Conclusion: In 20 yrs, "Y" is true.

    8% picked this

  3. Correct

    To be viable, a business

    Why this is right

    This provides a conditional (must = required idea, Right side), provides a factual premise saying the right side is true, and then concludes that the left side is true. Premise 1 X → Y Viable → Clear + cost-eff + pract + resp Premise 2 For thing A, Y is true. Your idea is (Clear + cost-eff + pract + resp) Conclusion For thing A, X is true. Your idea is Viable.

    Skill tested: Parallel Flaw · how this choice captures the argument's function is the move to repeat next time.

    66% picked this

  4. Those competitors—and only those—who meet

    Bad Premise Match Valid Logic

    The conditional rule supplied here is a bi-conditional rule. There's no such thing as doing an Illegal Reversal with a bi-conditional rule, because bi-conditional rules go in both directions. So we know right from the jump that this will be wrong. Bi-conditional wording: if and only if if but only if when and only when then and only then those and only those This argument says that "those competitors who meet the criteria are eligible. You meet the criteria, so you're eligible", which is perfectly valid logic.

    17% picked this

  5. A meal is nutritious only

    Different Flaw

    This provides a conditional and then attempts to reason via contrapositive logic: "the right side isn't true. Thus the left side isn't true." We're looking for Reversed Logic, in which the author says "the right side is true. Thus the left side is true." "Only if" = necessary / right side Nutritious → includes carbs and protein Contrapositive ~Carbs or → ~Nutritious ~Protein The argument is trying to say that "Since 80% of the calories in my lunch were from fat, I guess that means my meal didn't include carbs or didn't include protein. Thus my lunch was not nutritious." The flaw here is that even though 80% of the calories were from fat, it's still possible that the lunch included carbs, protein, or both. So the flaw is that the author hasn't fully established the contrapositive trigger. In the original argument, author fully establishes that the outcome is true and then illicitly concludes that the trigger is true. We wanted this Premise 1: X → Y Premise 2: For thing A, Y is true. Conclusion: For thing A, X is true. We got this Premise 1: X → Y Premise 2: For thing A, "Y" is not true. Conclusion: For thing A, X is not true.

    5% picked this

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