By what criterion did Karl Linnaeus systematize living organisms?

The question of the origin of species did not exist for him due to his belief in God. There are several signs or properties in the system. Thus, it turned out that completely unrelated organisms fell into the same class. It is worth noting the following: he divided all animals into mammals, birds, amphibians, fish, insects and worms, assigning an appropriate characteristic to each class.
He gave each animal a generic and specific Latin name. For example: Tit black (genus – tit, species – black).