Editing Logical biconditional (section)

===Biconditional introduction===
{{Main|Biconditional introduction}}
Biconditional introduction allows one to infer that if B follows from A and A follows from B, then A [[if and only if]] B.

For example, from the statements "if I'm breathing, then I'm alive" and "if I'm alive, then I'm breathing", it can be inferred that "I'm breathing if and only if I'm alive" or equivalently, "I'm alive if and only if I'm breathing." Or more schematically:

  B → A &nbsp;&nbsp;
 <u> A → B &nbsp;&nbsp;</u>
  ∴ A ↔ B

  B → A &nbsp;&nbsp;
 <u> A → B &nbsp;&nbsp;</u>
  ∴ B ↔ A