Lately, I have been learning about formal and informal logic. Today, I will share some notes on cause-effect related fallacies, which are unfortunately very common in arguments.
Post hoc, ergo propter hoc
Just because B happens after A, it doesn't mean that A caused B.
- My car has been working for 10 years. It just stopped working after I lent it to you last week, therefore you broke it.
Neglect of a common cause
A and B are correlated. It doesn't mean A causes B or B causes A. There could be a third reason C causing both.
- Two symptoms happen in the same patient, but both are caused by a third condition.
Take one factor and reach a conclusion using that only reason, ignoring all the other contributing factors.
Confusing of a necessary and a sufficient condition
Condition A is necessary for B if you can not have B without having had A.
- Oxygen is necessary for fire. This does not mean that everywhere there is oxygen there will also be fire.
Condition A is sufficient for B if anytime there is B, there has also been A.
- Winning lottery is sufficient to become a millionaire. But not necessary to become a millionaire, as there are other ways.
- I don't understand why the plant died. I watered it.
- Watering the plant is necessary but not sufficient.
Slippery slope fallacy (domino effect)
One small thing can follow a succession of fatal cause-effect chain, leading to a bad outcome.
- For want of a nail the shoe was lost.For want of a shoe the horse was lost.For want of a horse the rider was lost.For want of a rider the message was lost.For want of a message the battle was lost.For want of a battle the kingdom was lost.And all for the want of a horseshoe nail.
- One sip of beer can lead to wine, then to liquor, then to marijuana, then to heroin and then to the total ruin. Therefore, put down that drink.
- This sets a dangerous precedent...
This topic is really interesting to me and I will continue to explore other fallacies and human biases in the future.