Respond to Shuhan's objection:
I think Shuhan brought up a really good point. She pointed out that animals do not have the ability to use sentience to measure the worth of moral consideration. It seems that she suggested that every being should use pain and pleasure to judge whether others have moral consideration. But I think Peter Singer could argue that using sentience as a measure is only for humans but not for animals. Humans use the ability to sense pleasure and pain as a standard to judge whether a being deserves equal moral consideration. Animals do not need to consider whether they have a moral obligation to other animals so this does not apply to animals. This rule is created by humans and is used to regulate human behaviors but not apply to the whole nature.