There are two kinds of full powers: one deriving directly from the sovereign and the other from his deputies, that is to say, his ministers of state who have sufficient authority to nominate plenipotentiaries in his absence. Such powers are particularly desirable where the states lie far apart from one another. In such negotiations as those between the Court of Madrid and the Low Countries, or the different Italian states, the advantage of this procedure is obvious.... Passports are of course merely letters which establish the identity and good faith of the person as distinct from the representative of state, and they are given even in time of war in order to secure a safe passage between countries at war for ministers engaged upon negotiation which may lead to peace.... [Sidenote: _Instructions._] The instruction is a written document containing a statement of the principal intentions of the prince or the state; it is to be regarded as a general aid to memory and a general guide to conduct. It is secret and must be retained under the control of him who receives it, though of course there are occasions on which he will receive the command to communicate specific portions of it to a foreign minister or a foreign prince. Such communication is regarded as a rule as a mark of special confidence, but on the other hand it often happens that two instructions are given, one the ostensible, that is to say it is drawn up in such terms that it can be shown to other princes, and the other secret, which contains the true and final intentions of the prince himself. But even the latter type of instruction is subject to alteration by the daily despatches which the negotiator receives from home, and which ought to be read as so many new instructions drawn up in accordance with the reports which he has transmitted to his own court. It follows therefore that the manner of reports which a negotiator despatches to his home government will have a large influence upon the type of instruction which he receives from time to time. [Sidenote: _Oral Instructions._]