The letters to the Danish prince formed the basis of the 'Letters on Aesthetic Education', which were published in 1795 in the _Horen_, and constitute the ripest and most pleasing expression of Schiller's aesthetic philosophy. In the first ten of the 'Letters' he discusses the spirit of the age, for the purpose of showing that some sort of educational process is needed in order to fit mankind for the high calling of the freeman. The problem is to transform the state-ruled-by-force into a state-ruled-by-reason. To this end man must learn to resist and subdue the two inveterate enemies of his nobility, namely, the tyranny of sense which leads to savagery, and the inertness of mind which leads to barbarism, Schiller defines the savage as a man whose feelings control his principles, the barbarian as a man whose principles destroy his feelings. At present, he declares, the mass of men still oscillate between savagery and barbarism, but the man _comme il faut_ must establish and preserve a perfect equipoise between his sensuous and his rational nature. Whither shall he look for help? The state cannot aid him, for it treats him as if he had no reason; nor can philosophy save him through the mere cultivation of the reason, for it treats him as if he had no feelings. His only redeemer is the aesthetic sense, the love of beauty. The 'Letters' then take up the desperate task of showing how the aesthetic sense can do this wonderful work. Descending to the lowest nadir of abstraction,--Schiller calls it rising to the highest heights,--he brings up two ultimate instincts or bents of mankind, to which he gives the appalling names of the 'thing-bent' and the 'form-bent' (_Sachtrieb_ and _Formtrieb_). The former impels to a change of status, the latter to the preservation of personality. The one is satisfied with what is mutable and finite, the other demands the immutable and the rational. To harmonize these two instincts, to take care that neither gets the better of the other or invades the other's territory, is the problem of culture. For a driver of the ill-matched team Schiller calls in the _Spieltrieb_, or play-bent, which is only a new name for the aesthetic faculty. His idea is that in the moment of aesthetic contemplation the sensuous and the rational instinct both find their account. In the act of escaping from the serious pull of thought and feeling to a mental state which satisfies both without succumbing completely to either, he finds an analogy to the act of playing. At the same time he is careful to point out that this kind of play is different from the sports of common life. As he uses the word, it means surrender to the illusion of art. Play is thus the symbol of the highest self-realization. Only in playing is man completely man.