[99] At this time, however, the symbols of the inorganic world did not appeal to Froebel with the same force as those of the organic world. In a letter to Madame von Holzhausen. 31st March, 1831, he writes: "It is the highest privilege of natural forms or of natural life that they contain agreement and perfection within themselves as a whole class, while differing and filled with imperfection in particular individuals; for look at the loveliest blooming fruit-tree, the sweetest rose, the purest lily, and your eye can always detect deficiencies, imperfections, differences in each one, regarded as a single phenomenon, a separate bloom; and, further, the same want of perfection appears also in every single petal: on the other hand, wherever mathematical symmetry and precise agreement are found, _there is death_". [100] Not a figure of speech altogether; for Froebel did really decline a professorship of mineralogy which was offered him at this time, in order to set forth on his educational career. [101] That is, putting development into a formula-- Thesis-+-Antithesis | Synthesis. The true synthesis is that springing from the thesis and its opposite, the antithesis. Another type of the formula is this-- Proposition-+-Counter-proposition | Compromise. Understanding by "Compromise" (_Vermittlung_) that which results from the union of the two opposites, that which forms part of both and which links them together. The formula expressed in terms of human life, for example, is-- Father-+-Mother | Child. Philosophic readers acquainted with Hegel and his school will recognise a familiar friend in these formulae. [102] Froebel travelled from Berlin to Osterode, and took with him both his brother Christian's sons, Ferdinand and Wilhelm, to Griesheim; there to educate them together with the three orphans of his brother Christoph, who had died in 1813, of hospital fever, whilst nursing the French soldiers. Of the sons of Christian, Ferdinand studied philosophy, and at his death was director of the Orphanage founded by Froebel in Burgdorf; Wilhelm, who showed great talent, and was his uncle's favourite nephew, died early through the consequences of an accident, just after receiving his "leaving certificate" from the gymnasium of Rudolstadt.