CSCI 1 Week 3 Day 1 - Conditionals and Lying
2Broadcasted today from a laptop, please pardon the quality of the stream.
We talked about logical implications today, which come up all the time in programming and real life - "If you write an app for me, then I will give you 10% of the company" is the sort of thing business people consider to be generous, despite you doing all the work, and is a conditional. It doesn't say what will happen if you don't do the work. Just that if you do the work, you'll get 10% of the partnership.
In logical terms, we say 'x implies y' where x is you writing an app, and y is them giving you 10% of the company. There's a couple ways this can pan out:
1) You write the app for them and they give you 10% of the company
2) You write the app for them and they don't give you 10% of the company (i.e. they lied)
3) You don't write the app and they don't give you 10% of the company
4) You write the app and they give you 10% of the company
The only time when they lied is case #2, where you did X but they failed to do Y. In all three other cases the business guy told the truth.
There's four arguments that could be made about this deal if you know the business person is telling the truth, two of which are valid inferences, and two of which are fallacious (invalid):
1) If you did the work, then you got 10% of the company (valid, deductive inference, modus ponens)
2) If you did not get 10% of the company then you did not do the world (valid, deductive inference, modus tollens)
3) If you did not do the work, but from this fact someone deduces you didn't get 10% of the company (invalid inference, since the businessman did not say what he'd do if you don't do the app, perhaps you earned your 10% another way, this is a fallacy called denying the antecedent)
4) If you got 10% of the company and someone infers that you did the work (invalid, again you could have earned the 10% another way, this is a fallacy called affirming the consequent)