if you don't ever -- or indeed often -- find yourself needing to zig when, not only other people, but all kinds of internal "voices" in your mind are loudly shouting for you to zag, then you're either a native rationalist...

Shouldn't this start with "if you frequently..." ?

Can anyone explain why Goodman considers this statement to be true:

Hence `If that piece of butter had been heated to 150°F, it would not have melted.' would also hold.