| Description: A proposition is testable
iff its negative or double-negative is true.
See Chapter 2 [Moschovakis] p. 2.
We do not formally define testability with a new token, but instead use
DECID  before the formula in question. For example,
DECID    corresponds to " is
testable". (Contributed
by David A. Wheeler, 13-Aug-2018.) For statements about testable
propositions, search for the keyword "testable" in the comments
of
statements, for instance using the Metamath command "MM> SEARCH *
"testable" / COMMENTS". (New usage is
discouraged.) |
DECID 
