In it, he outlined his ideas for the hierarchical classification of the natural world, dividing it into the animal kingdom (regnum animale), the plant kingdom (regnum vegetabile), and the "mineral kingdom" (regnum lapideum).
Nel expoñía as súas ideas para a clasificación xerárquica do mundo natural, dividíndoo nos clásicos tres reinos, o reino animal (Regnum animale), o reino vegetal (Regnum vegetabile) e o "reino mineral" (Regnum lapideum).