PHIL 105 Lecture Notes - Lecture 4: Propositional Calculus, Qi, Modus Tollens

• School: Simon Fraser University
• Department: Philosophy
• Course: PHIL 105
• Professor: Jill Mc Intosh

Document Summary

Two requirements for an argument to be good (rationally be strong for you): Its premises must be reasonable for you to accept. An argument whose premises, if true, would support its conclusion, is well formed . An argument is well-formed only if it is valid or cogent. An argument is valid if its premises are true, its conclusion must be true. My van is parked where i left it or my van has been stolen. An argument is cogent if its premises are true, they provide reason to think the conclusion is true, but they could be true yet the conclusion false. Most students in this room are under 25. The person in the top left seat is a student in this room. Whether or not an argument is valid is simply a matter of its form! In some cases, we can use sentential logic. My van is parked where i left it.