Latin: Inauspicious. Applied, in the Roman law, to a day on which it was unlawful to open the courts or administer justice. Negatio conclusionis est error in lege. Wing. 268. The denial of a conclusion is. error in law. Negatio destruit negationem, et ambae faciunt affirmationem. Lord Coke cites this as a rule of grammatical construction, not always applying in law. Negatio duplex est afflrmatio. A double negative is an affirmative.