The Little Blue Reasoning Book - Brandon Royal [44]
Tip #25: Representativeness assumptions are based on the idea that some smaller factor is representative of the larger whole.
Tip #26: Broadly speaking, representativeness assumptions occur anytime that we argue from the particular to the general.
Tip #27: Check to see if evidence has been handpicked to support a claim being made. Otherwise we may fall victim to “proof by selected instances.”
Tip #28: “Evidence omitted” may hold the key to determining an argument’s validity.
Tip #29: Correlation does not equal causation.
Tip #30: Cause-and-effect assumptions are grounded in the idea that because one event follows another in time, the first of the two events is the cause and the second is the effect.
Tip #31: When tackling cause-and-effect scenarios, think first in terms of alternative causal explanations. If the argument states that A is causing B, then check to see that another cause, namely C, is not instead causing B.
Tip #32: A more complex form of alternative explanation occurs when two effects result from a single cause. Thus, if an argument suggests that A is causing B, consider the possibility that another cause, namely C, could be causing both A and B.
Tip #33: If A is thought to be causing B, the idea that B is causing A is called reverse causation and casts serious doubt on the notion that A is really causing B.
Tip #34: Test the opposite scenario — if you hear that a full moon causes the crime rate to rise, always ask what the crime rate is like when the moon is not full.
Tip #35: Theory may be divorced from practice. Plans may not equal completed action. Do not assume that plans will be implemented without a hitch.
Tip #36: “Can” does not equal “will.” The ability to do something should not imply application of that ability, whether due to choice or neglect.
Tip #37: One way to uncover implementation assumptions is to anticipate bottlenecks.
Tip #38: An argument may depend on the assumption that a person or organization is aware of a pre-existing fact, situation, or condition.
Tip #39: Searching for something does not guarantee that we’ll recognize it once we’ve found it. The ability to accurately identify that which we are seeking to find may be a key assumption.
Tip #40: Always look for potentially vague terms in an argument and ask for or seek clarification.
Chapter 5: Mastering Logic
Tip #41: Be careful not to reverse the flow of “If … then” statements. “If A, then B” is not the same as “If B, then A.” This is known in logic as the fallacy of affirming the consequent.
Tip #42: The statement “If A, then B” leads to the logical inference “If not B, then not A.” This is known in logic as the contrapositive.
Tip #43: The statement “If A, then B” does not equal “If not A, then not B.” This is known in logic as the fallacy of denying the antecedent.
Tip #44: One way to think about an “If … then” statement in the form of “If A, then B” is that just because A leads to B does not mean that C, D, or E could not also lead to B.
Tip #45: Necessary conditions are not the same as sufficient conditions. The statement “A person needs water to remain healthy” does not mean that water alone is enough to keep a person healthy. Water is a necessary but not sufficient condition for someone to remain healthy.
Tip #46: The statement “If A, then B” does not equal “Only As are Bs.” For example, the statement “If one wants to make a good salad, one should use tomatoes” should not be interpreted to mean that only tomatoes are necessary to make a good salad.
Tip #47: The statement “Every A is a B” does not equal “Only As are Bs.” For example, the statement “Every cat is a mammal” should not be interpreted to mean that “only cats are mammals.”
Tip #48: “All” statements imply inclusivity; “some” statements imply crossover; “no” statements imply exclusivity.
Tip #49: Whereas “some” statements imply reciprocality, “most” statements do not necessarily