As Singer says, "In each case we must look at the nature of the creature and its nervous system. In some cases a decision will be difficult to reach, but this is no more an argument against my position than the parallel difficulty of saying when a person is bald is an argument against the existence of baldness"( Singer, 1985 ). Like human equality, animal equality does not mean equal abilities. It means that all animals have an equal right to moral consideration and legal protection. In Singer`s view, if a being is capable of suffering, there can be no moral justification for refusing to take that suffering into consideration. No matter the nature of the being, the principle of equality requires that its suffering be counted equally with the like suffering of any other being. It is true, of course, that we cannot know exactly how animals suffer. I n the animal rights view, the question is not merely whether an animal suffers as a consequence of any particular animal use. The question is whether humans have the right to exploit other sentient beings for any purpose as a means to an end even if a particular type of animal use is considered "humane" by the traditional definition. The fact that the animal has the capacity to suffer is sufficient to make its use unacceptable. One opposed to this view would argue that if all animals are ought to be considered equal, than a moral agent ( duties toward other individuals and society as a whole ) must consider responsibilities that include all systems of evolution, such as soil, plants and, land. Because of its emphasis on the prevention of animal suffering, some environmental philosophers criticize Singer as, at best, falling short of the appreciation of predation that any adequate environmental ethics must exhibit. Gary Constock has expressed this point well: " Even a philosopher could observe, given a little experience, that the interests, drives, needs, purposes, wants and desires of animals differ according to their genetic make up and social conditioning.