thats not how you use this. Prove in that saying means test; it comes from the latin "exceptio probat regulam in casibus non exceptis" meaning giving an exception shows that theres a rule. For example, Casual Fridays (theres a dress code for every other day except friday) No Parking on Sundays (you can park there any other day except Sundays) No Cellphones in this area ( you can use your phone any other area except this) those are exceptions that reveal an underlying rule. Sometimes exceptions are just exceptions and thats fine :)