Let's take driving on the roads. We all have a licence to drive, to some adequate driving level. Imagine you can quantify/measure this driving ability, that includes reaction times etc.. We have scales for the likes of earthquakes, me mineral hardness etc.. So pick a driving ability scale and you devise a test to figure out a drivers score. It could encompass adherence percentage to the Highway Code, reaction time etc.. and it's scaled 1 to 10, 10 being the best. Person A's alround driving skill/ability is a 5. Person B is a brilliant driver, super fast reaction time etc.. and is a 10. Now person B has a couple of beers and is breathalyzed at the side of the road. Oh dear, he's over the limit so he's arrested. If he immediately took the driving scale test, he scores a 6. But he's still a better and safer driver than person A, so what is he really charged for? (By the way, I've never drink drive or condone it, it was a discussion point I had between friends).