Jim's teacher asked him to determine whether a sample of a substance contained iron. ███ ████ ████ ███████ ███████ █████ ██ ██ ██████ █ ██████ ████ ███ ██████████ ███ █████████ ████ ███ █████████ ███ ███████ █████ ███████ ███ █████████ ██████ ████████ ██ ███ ███████
Jim concludes that a substance contains iron because it’s attracted to a magnet, and iron is a material that’s attracted to magnets.
This is a cookie-cutter example of an argument mistaking a sufficient condition for a necessary condition. Jim treats “containing iron” as though it were a necessary condition for being magnetic, even though it’s only sufficient. In other words, he ignores the possibility that the substance contains a magnetic material other than iron.
Jim's reasoning is questionable in ████ ██ █████ ██ ████████ ███ ███████████ ████
iron sometimes fails ██ ██ █████████ ██ ███████
iron is attracted ██ █████ ███████ ███████ ███████
the magnet needed ██ ██ ████████ ██ █ ███████ ███
magnets attract substances █████ ████ ████
some magnets attract ████ ████ ████████ ████ ██████