It was usual in the Middle Ages to discriminate between good and evil animals, to ascribe to them human qualities and to combine these symbolically with biblical themes. Lions and Eagles symbolize strength. The origin of this symbolism is a book full of quotations from the Philosopher Aristoteles, known as the Physiologus. This is the reason that he and Plato are included in the Animal Cycle. This is proof that there was at this time at least one gifted intellectual in Esslingen, who conceived these unique designs. Perhaps it was the physician and writer Trutwin.