 The difference between humans and animals is still characterized by Condillac as difference of degree. For example, animals have a natural language of action, just like humans, and they use it to communicate with each other their needs and to help each other. The signs of this language vary among different species not only according to the different ideas they have but also according to the variety of organs (external conformation) they possess, since these organs condition the way ideas can be expressed. Animals of different species whose external conformation resembles each other can communicate with each other, at least to a certain extent: Condillac describes the case of dogs that can go as far as understanding not simply the language of action but also the language of articulate sounds of humans. But animals whose external conformation is widely different from ours cannot communicate with us, as the case of the parrot shows: it can articulate sounds, but both his ideas and his language of action is widely different from ours (Treatise of Animals II.4).