Cutting against the grain. When anyone attempts what he is totally unqualified for, he may be said to, be labouring without the assistance of Minerva, the reputed goddess of wisdom, natura repugnante, against nature. «Quam quisque norit artem, in hac se exerceat», let everyone confine himself to the art in which he has been instructed, or Which he has particularly studied. En casa del moro no hables algaravia. Do not speak Arabic in the house of a Moor, lest, instead of gaining credit, you only expose your ignorance.