This Warning alerts us to the fact that when treated as a rewrite
rule, the new rule
TRIVIAL-CONSEQUENCE, rewrites terms of the same form
as a rule we have already proved, namely
When you see this warning you should think about your rules!
In the current case, it would be a good idea not to make
TRIVIAL-CONSEQUENCE a rule at all. We could do this with
ACL2 proceeds to try to prove the theorem, even though it printed some warnings. The basic assumption in ACL2 is that the user understands what he or she is doing but may need a little reminding just to manage a complicated set of facts.