For Section A05 (Friday 11-11:50 AM)

[William Albuquerque]

Hi Section A05,

 

Sorry for the confusion at the end of class! This is the risk of trying to come up with examples too fast. Although the original argument I wrote was invalid, the argument I actually meant to present was the following:

 

1. If x wins the electoral college, then x is president.

2. x is president

 

Therefore, x won the electoral college

 

THIS argument has the counter-example I intended; namely, presidents who did not win the electoral college (e.g. LBJ). Notice that even if (1) and (2) were true, the conclusion could be false, because there could be a president (and, in fact, there were) that didn’t win the electoral college. This is because there are other ways to become president (e.g. assassination), and premise (1) does not state that winning the electoral college is the only way to become president. Thus, the argument is invalid. 

 

Hopefully that clears things up! The important point to remember is just that a valid argument must have a necessary relation between the premises and the conclusion; meaning that if the premises are true, the conclusion must be true. Remember that this (conditional) relation can still hold even if the premises are actually false. Only soundness requires truth of premises. 

If you have any questions, feel free to email me at walb...@ucsd.edu .