Wednesday, January 11, 2012

No Spiders Are Insects (No Spider Logic)

m]  Spiders can’t be insects because they are eight-legged.

n]   All spiders are eight-legged.
      No insects are eight-legged.
      No spiders are insects.   


1.  Top:  Odilon Redon, Smiling Spider, 1891.

2.  Bottom:  Odilon Redon, Crying Spider, 1881.

3.  Text excerpted from:  Logic by Wesley Salmon (Englewood Cliffs, Prentice-Hall, 1973).


  1. I'm in a waiting room and only have a couple of minutes. Is this by the same person that wrote All Whales are Mammals?

  2. Yes. From the same book. Hope your wait is a short one. Curtis