Doctor Moreau's island is an allegory for the role organized religion plays in broader society. Moreau is a creator, like God. The Beast Folk so believe in his power that Prendick is able to convince them that when Moreau dies, he has really left his body so that he can observe the goings-on on the island from on high. He is also a king, making and enforcing the Law the Beast Folk must follow. His dual role as God and king represents the ways Christianity functions as the original foundation for much of the law in England and elsewhere in the world. Although England's political structure had gone through some periods of upheaval, the basic structure of the monarchy meant that for centuries, kings and queens supposedly chosen by God had been making laws that pointed back to Christian beliefs about right and wrong. Victorian society and Moreau's island alike seem to be entirely dependent on inhabitants' willingness to buy into a fixed set of rules set forth by Christianity and those who use it to maintain political power.
Moreau and Montgomery's paranoid imposition of the Law, a kind of catechism that the Beast Folk must repeat over and over to affirm Moreau's power over them, raises the question of what natural impulses laws and religious practices prevent humans from following. There is a real sense on the island that the Beast Folk will descend into violence if they are not restrained by their faith in the Law. Humans, too, are restrained by religious commandments and laws (for example, not to kill). What would happen if humans were left to their own devices, and if we were left to develop our own belief systems?
Moreau himself is one answer to this question. In exile, he exercises his power to its fullest extent, morals and ethics aside. He develops his own Law, which is a naked attempt to keep the Beast Folk under his thumb. The Beast Folk have not necessarily internalized a sense of morality from the Law, anymore than Moreau has internalized a sense of morality from living in Victorian society. Instead, they demonstrate how religious and social rituals can train animals and humans alike into performing good manners.
In fact, the way the Beast Folk become human-like and then descend into animal violence makes them more horrifying than if they had simply remained animals. As animals, they were innocent. By making them partly human, Moreau gives them the chance (like Adam and Eve in the Garden of Eden) to become corrupt and fall from grace. Because Moreau imposes the Law rather than teaching the Beast Folk how to uphold their own morality, the Beast Folk immediately descend into chaos when the Law is broken. The novel ultimately seems to conclude that humans have a greater moral responsibility toward their neighbors than animals do, but that organized religion and strict laws actually keep humans from understanding and managing their own responsibility. Unless we all want to become like Doctor Moreau when given the chance, Wells thus suggests, we must learn a deeper sense of ethics than organized religion instills.