| Description: Rule of Modus Ponens. 
The postulated inference rule of propositional
       calculus.  See e.g.  Rule 1 of [Hamilton] p. 73.  The rule says, "if
       φ is true, and
φ implies ψ, then ψ must also be
       true".  This rule is sometimes called "detachment", since
it detaches
       the minor premise from the major premise.  "Modus ponens" is
short for
       "modus ponendo ponens", a Latin phrase that means "the
mode that by
       affirming affirms" - remark in [Sanford] p. 39.  This rule is similar to
       the rule of modus tollens mto 167.
 
       Note:  In some web page displays such as the Statement List, the
       symbols "& " and "⇒
" informally indicate the relationship
       between the hypotheses and the assertion (conclusion), abbreviating the
       English words "and" and "implies".  They are not
part of the formal
       language.  (Contributed by NM, 30-Sep-1992.)  |