Logical Fallacy

* argument from incredulity (I find it hard to believe, therefore it can't be true)
* ad hominem
Logical Fallacies
    Ad hominem, when you insult a person rather than tackle an argument you have already failed.
  "if"  ~ just because the outcome is 'C', it does not infer that it came from 'A'.
     e.g.  A -> C
           B -> C

  "if and only if"
     necessary   sufficient
Fundamental Theorem of "Exclusive OR":
   any missing column can be derived from the remaining two.

if and only if (bijection)