Denying the Antecedent


    Any argument of the following form is invalid:
    If A then B
    Not A
    Therefore, Not B
  1. if you get hit by a car when you are six then you will die young. But you were not hit by a car when you were six. Thus you will not die young. (Of course, you could be hit by a train at age seven, in which case you still die young.)
  2. If I am in Calgary then I am in Alberta. I am not in Calgary, thus, I am not in Alberta.
    Show that even though the premises are true, the conclusion may be false. In particular, show that the consequence B may occur even though A does not occur.
    Barker: 69, Cedarblom and Paulsen: 26, Copi and Cohen: 241

26 May 1995