Conditional Statements

[Wonderful22]

When the phrase "if and only if" is used, is it indicating the necessary or sufficient?

[Dave Killoran]

Both, actually!

The "if" is sufficient, and the "only if" is necessary. So, when you start with this:

• D if and only if J.

It really can be broken into two sub-statements:

• D if J
  
  and
  
  D only if J

Each sub-statement then can be diagrammed individually:

• D if J = J D
  
  and
  
  D only if J = D J

Combined, that becomes:

• D J

Please let me know if that helps. Thanks!