According to the Roman idea, spying was accounted a fair stratagem in both war and politics and was, in theory at least, distinguishable from treachery. Between the two acts there is, of course, a real difference, although in works dealing with international law the terms are often confused, some writers treating them as interchangeable, whilst others but loosely differentiate between the act of spying and that of betrayal, the presumption always remaining that the man who is capable of being a successful and voluntary spy also possesses talents which are common to the elemental traitor. The penalty of death, says Bluntschli, should be such as to terrify all spies, and it is the custom accordingly to execute them ignominiously by hanging. Technically the spy has been defined as one who clandestinely goes in quest of information, whilst a traitor is one who spies within his own community and to its undoing. Although most authorities agree in considering espionage as lawful among the ruses of warfare, all, with one exception, concur in determining that death remains the only logical desert of the man who has possessed himself of secrets upon which the common safety depends. Certain international jurists have objected to the employment, in any cause, of spies, as being immoral, or as condoning acts which are of themselves immoral, and the French writer Morin looks upon espionage with particular horror on the ground that it is "usually malice aforethought and is never voluntary," a peculiar enough view. It is especially blameable, he holds, because a premium is placed upon essentially dishonest dealing, although he admits, with some inconsistency, that it may sometimes become lawful—when it is unsoiled by perfidy, as he puts it. Only the last emergency can at all justify it, says Morin, who is singular in declaring that a spy should not be put to death unless caught in the act. Napoleon himself displayed an unexpected leniency wherever possible towards captured spies, and this on the ground, as he said, that the spy is, by his nature, a base character. In the opinion of the great soldier the best spy is the half-breed who is a natural cosmopolitan and is consequently unaffected by ideas of patriotism. His greatest spy, Schulmeister, was a man of decidedly mongrel antecedents and began life as a smuggler. Pedlars he also declared to be invaluable in espionage, and for the reason that they are naturally disposed to vagabondage, itself a trait of degeneracy. It is well known that he would only employ in such work men whose past had been soiled by some act of a disgraceful or criminal kind, and like the great Frederick, it was his custom to propose to actually convicted criminals their enlargement as the reward of a successful piece of spying.