It is a just remark of Cicero's, that the language of logic is not that of daily and familiar intercourse: the writers of that class have phrases peculiar to themselves: which indeed is the case with arts of every description. So in treaties, where military arrangements occur, an army is defined to be a number of soldiers capable of OPENLY invading a foreign, or an enemy's country. For historians everywhere make a distinction between the private incursions of robbers, and what is done by a lawful and regular army. What constitutes an army must be therefore judged of by the enemy's force. Cicero defines an army to consist of six legions and auxiliaries. Polybius says, that a Roman army in general amounted to sixteen thousand Romans, and twenty thousand auxiliaries. But a military force might be composed of a less number of troops than this. In the same manner the number of ships sufficient for any purpose will amount to a fleet, and a place able to hold out against an enemy may be called a fort. IV. It is necessary to make use of conjecture, where words or sentences admit of many meanings: A mode of expression when included in one word, is called by Logicians, a synonymous term, and, when extending to two or more words, a doubtful phrase. In the same manner it is necessary to have recourse to conjecture whenever a seeming contradiction occurs in the expressions of a treaty. For in that case we must try to discover such conjectures, as will reconcile, if possible, one part with another. For if there be an evident contradiction, the contracting parties by their latter determinations, must have intended to abrogate their former; as no one can design to make contradictory resolutions at the same time. Indeed all acts depending upon the human will, as in the case of laws and testaments, which depend upon the will of one party, and in contracts and treaties, which depend upon that of two or more, all these acts are liable to changes, with a subsequent change of will in the parties concerned. In all such cases any obscurity in the language obliges us to have recourse to conjectures, which are sometimes so obvious, as to point out a meaning directly contrary to that of the words in their usual acceptation. Now the principal sources of conjecture are to be found in the subject-matter, the consequences, and the circumstances and connection. V. From the subject or matter, as for instance, in the word day. Thus if a truce be made for thirty days, here civil and not natural days are meant.[46]