A

Latin. From the impossibility of a thing to its nonexistence, the inference follows necessarily in the negative. That which cannot be done is not done. 

6. A non posse ad non esse sequitur argumen tum necessario negative , licit non affirmativeLatin. If a thing be not possible , an argument in the negative may be deduced , namely , that it has no existence ; but an argument in the affirmative cannot be deduced , namely, that if à thing is possible it is in existence.