The conflict between the right-handed brother and left-handed brother described in "The World on Turtle's Back" shows that the Iroquois most likely believed

The brothers’ opposing natures and their lifelong conflict represent a larger struggle between good and evil. This suggests the Iroquois believed that good and evil are in constant opposition, rather than that left-handed people are evil or should be treated differently. The best answer is “there is an eternal battle between good and evil.”

AI-written and checked against the verified answer.