In the 'Letters upon Don Carlos', published in 1788, in Wieland's _Merkur_, Schiller undertook to defend himself against his critics and to correct some misapprehensions. In temper and style they are admirable, even when they do not convince. They begin by admitting and accounting for that seeming incongruity between the first three and the last two acts, which has always been the gravamen of critical objection to 'Don Carlos'. After this they attempt to show that such a character as Posa might very well have existed in the sixteenth century at the Spanish court. Then we are told that it was not the author's purpose to depict Carlos and Posa as a pair of ideal friends. For Carlos, indeed, friendship is everything, but not for Posa. In him the passion for friendship is everywhere subordinated to the passion for humanity. He is not to be blamed, therefore, for belying the character of a true friend, since that is not his dominant and essential character. He regards Carlos merely as an indispensable tool for his political designs. In his interview with the king he is carried away by a momentary enthusiasm,--what he says there is of no importance, his hopes being really fixed upon Don Carlos. At the beginning of the fourth act he sees not his personal friend, but the instrument of his political plans, in awful danger. He resolves to save him for Flanders and for humanity by sacrificing himself. This is no more unnatural or inconceivable than the self-sacrifice of Regulus. But Posa wishes to save his friend like a god and not like a common level-headed Philistine. He has the soul of a Plutarchian hero, and where two ways present themselves, the most natural is for him the most heroic. Hence his desperate procedure and its disastrous consequences. To all of which one can give but a qualified assent, the difficulty being that the play is not so constructed as to bring out its author's intention. The character of Posa in Act IV is a surprise, and a disagreeable surprise. His conduct may harmonize with a theory of antique heroism, but it does not grow naturally out of what precedes. There is no exigency that calls for his heroic foolhardiness. The reader or the spectator can hardly be supposed to know that the famous tenth scene in the third act, the longest and most carefully elaborated in the whole play, does not count. One naturally supposes that it does count, and the only way it can count is to create a hopeful situation of which Posa is absolute master. When, therefore, he throws away his advantage and deliberately plunges his friend into a needless danger, in order to make an opportunity for rescuing him at the cost of his own life, one inevitably associates him mentally not with antique heroes but with modern lunatics.