They have a brain.

But it isn't REASON!" "You mean--" he cried.
"That you, a man, unarmed, alone, are still their master," she interrupted him.

"In the face of reason they are powerless.

See, there comes Metoosin with the frozen fish! What if he were a stranger and the fish were poisoned ?" "I understand," he replied.

"But others drive them besides you ?" "Only those very near to the family.