Lesson 5: Logical Laws, Principles, and Some More Fallacies

Lesson 5: Logical Laws, Principles, and Some More Fallacies

​3 Laws of Logic

1. The law of identity - ​

   (x infers x or x is x)

2. ​The law of contradiction - it is impossible for to be true.

3. ​The law of excluded middle - In

   one of these must be true.

​Necessary v. Sufficient Conditions

​Necessary Conditions - Conditions which must be in place in order for success to be achieved.

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​Sufficient Conditions - Conditions which are enough to achieve success, but are not necessarily the only path to success.

​Occam's Razor

​Occam's Razor - All things being equal, if there are two or more theories that explain some phenomena, the simplest, and fewest, explanations that sufficiently cover every phenomenon is the best explanation.

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Hanlon's Razor - Never attribute to malice what can be attributed to stupidity.

Multiple Choice

You can get an A in my class if you get an A on every assignment. This is an example of a...

• sufficient condition

• necessary condition

Multiple Choice

It is hot and cold is an example of a violation of the law of...

• contradiction

• identity

• excluded middle

Multiple Choice

_____________ Razor states that the simplest theory or answer is preferable if two or more theories equally explain some phenomena.

• Occam's

• Hanlon's

​Ad Hominem

A personal attack on an interlocutor rather than a logical assertion about their argument.

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​Someone being a felon, a Democrat, or a Christian does not necessitate that their arguments are bad or wrong.

​Halo (or Devil) Effect

​The Halo Effect is when we attribute unrelated positive traits to something or someone due to one positive trait.

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​The Devil Effect is when we attribute unrelated negative traits to something or someone due to one negative trait.

​Post Hoc Ergo Propter Hoc

​A Post Hoc fallacy is a causal link where none may exist. In order to avoid post hoc fallacies, we need to be positive that something which follows another event is truly caused by that event.

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​Post hoc ergo propter hoc means "after this, therefore, caused by this."