Thomas Wells states that Singer's call for ending animal suffering would justify simply exterminating every animal on the planet in order to prevent the numerous ways in which they suffer, as they could no longer feel any pain. Wells also stated that by focusing on the suffering humans inflict on animals and ignoring suffering animals inflict upon themselves or that inflicted by nature, Singer is creating a hierarchy where some suffering is more important than others, despite claiming to be committed to equality of suffering. Wells also states that the capacity to suffer, Singer's criteria for moral status, is one of degree rather than absolute categories; Wells observes that Singer denies moral status to plants on the grounds they cannot subjectively feel anything (even though they react to stimuli), yet Wells alleges there is no indication that nonhuman animals feel pain and suffering the way humans do.