Haeckel says: The oldest source of sexual love is found in the erotic chemotropismus, in the attraction the male and female sexual cells are exercising upon each other. This sexual affinity is found even in the lowest stage of plants as in the protophyts, where both cells swim toward each other to unite. Rosenkranz finds in nature only an empire of love, of a love that penetrates all things and leads them to a common end. Gravitation is love dominating nature. Organic life is a continued phenomenon of love. Even in inorganic nature the combination of substances, one with the other, is a trait of love. The appearance of heat and the flash of light that accompany the chemical process are, in a manner, the heralds of lust felt by the substances while uniting. Love of the sexes is a love for things that is ignored and unknown and which is not yet even in existence. The lovers must perish that love may continually rise to new life; the individual dies that the species may live. Love is not the aim but the means, serving life and development. Love is the joy at another’s existence and is stronger than the delight at one’s own existence. Love transforms the nuptials into a jubilee even where it is the eve of death. It is hence as strong as death. There exists not only a natural love, but also a spiritual love which is stronger than death. Natural love is not the true love, but only a stepping-stone. True love is no longer blind and necessary, but conscious and free. Teichmüller says: In sensual love, Nature makes use of the individual only incidentally, by making the propagation of the species a personal concern of the individual. She gains her end by a mystification. The individuals, by virtue of the innate impulse, consider the external aim of nature as their own personal concern, for which they voluntarily hazard everything, even life itself. Teichmüller further claims that in physical love only the state of irritability and the sensibility of the nerves of the subject are important. The object is only concerned as a soliciting casualty. The natural impulse cannot aim at lust, for lust is not an end, but only expresses the coördinate state of the subject during the actions. Every desire aims at a specific action as its end. The musician does not long for lust but for music. The pleasure connected with it ensues coördinately with the success of the performance. Of sentimental love, Teichmüller says, the individual loves an ideal which it has itself created in its thoughts and fancy and with which the actual need not harmonize at all. For that reason the “treasure” (in German the lovers call each other “Schatz” or treasure) lies not without but within the lover. The beloved person outside is only the key that understands to unlock the treasure. The key is not able to create the wealth. Whoever is poor and desolate within, for him no key can unlock the treasure of love.