But let me not be misunderstood, there is all the difference between the attempt to debauch the subjects of a sovereign prince in order to ensnare them in conspiracy against him, and the legitimate endeavour to use every opportunity for acquiring information. The latter practice has always been permissible, and indeed is a necessary part of diplomacy. No criticism can fall upon a foreign envoy who successfully adopts the practice; the only culprit in such a case is the citizen of a foreign state who from corrupt motives sells information abroad. Apart from considerations of international law the interest of the public peace demands the preservation of the privileges of foreign envoys, for otherwise wars would be even more frequent than they are, because no prince would permit insults to his ministers to go unavenged. They are rightly resented, and the prince may pay heavily in his own peace of mind and the repose of his subjects for a moment of passion. He need do no more, however, than demand satisfaction for the bad conduct of any foreign envoy, and if he has just cause of complaint he will probably receive it. In any case the dismissal or recall of an ambassador will be read as a pointed lesson to all his colleagues in diplomacy, who will then understand that the price of evil conduct is the humiliation of dismissal. [Sidenote: _The Credentials of an Ambassador._] When an ambassador is sent to a foreign court, his master gives him a letter addressed to the foreign prince requesting him to give the same credence to the bearer of the letter as to its writer. This despatch is called a letter of credence, which thus establishes the identity of its bearer and stands as the hall-mark of his office. In France there are two sorts of letters of credence: one called _Lettre de Cachet_, which is despatched and countersigned by the Secretary of State for Foreign Affairs, and sometimes also called _Lettre de la Chancellerie_. The other is written by the hand of one of the royal private secretaries, and signed by the King himself; it is countersigned by any minister, and is usually handed direct in private audience to the foreign prince to whom it is addressed. The former type of letter is presented in ceremonial public audience. When a negotiator is appointed by his prince to a free state or an assembly, which for this purpose is treated as though it were a court, he does not receive letters of credence, but his character and identity are fully established in his full powers, which he must exchange with ministers on arriving. The document known as full powers is an authorisation by the prince to his representative abroad to undertake all kinds of public business, the results of which the sovereign himself agrees to accept by the proxy of his minister; but as a rule in such full powers the particular matter under discussion is carefully specified, and the authority to act is confined to it. [Sidenote: _Full Powers._]