An assertion which is default true is assumed to be true in all cases, unless there is evidence to the contrary. Thus, unlike an assertion which is monotonically true, it has exceptions. It is represented in the Cyc Browser by a yellow ball. By default, every assertion in Cyc can be given an exception, or can be marked with the predicate #$hasExceptions, to indicate it is default true. When an assertion has been declared to never have exception with #$willNeverHaveExceptions, it is not possible to give it exceptions.
