In Animal Liberation , Peter Singer claims that people should expand the scope of moral concerns (Llorente, 2009, 61) , and pay more attention to animals' lives and feelings. He believes that animals also have feelings. Based on two basic principles, including principles of equality and utility, Singer draws the conclusion of "sensualism". In other words, he believes that all creatures who can feel the sense of pain, should endow with the same moral concerns. Apparently, animals also enjoy the ability to feel painful. Indeed, on account of what is now known, if human infants' potential is not taken into consideration, they do not have a higher level of spiritual characteristic compared with other adult animals. Therefore, animals should also get equal moral concerns.
Singer claims that specicism is quite similar to racism, because he discovers there are many factors in common between them. First of all, there are hierarchies in both specicism and racism. When it comes to racism, people will immediately come up with black slaves and some other groups. It is clear that people would categories themselves into different groups. In the slavery era, people tended to believe that black people were inferior to the white, and their lives were more valuable than black people', even though they were all human-beings. They just simply divided people into different groups according to their colors. Also, specicism also refers to that hierarchy between creatures. Human beings believe that they are superior to other animals. Hence, people tend to treat them as pets, foods and even experimental models, even if they also have feelings. And the hierarchies make people be fully of unknown superiority, and feel that they have rights to dominate other' lives. Therefore, the white would tend to look down upon the black, just because of their different colors. And human beings are more likely to despise other animals, who are with less wisdom. Besides that, specicism and racism both represent the unequal treatment and persecution between different groups (Llorente, 1978, 249) . Because of racism, many peoples would treat other peoples as "inferior" ones. During the era governed by Nazi, there were countless cruel experiments conducted in Germany. Many famous doctors utilized "inferior" Jewish, Russian and Polish peoples as experimental models to prove their ideas, and get some knowledge from these experiments. Nowadays, people would like to use animals as experimental models to get some knowledge, just because they are "inferior" to human beings. And this can be named as specicism, which is quite similar to racism, because the "inferior" groups would both be treated unequally and cruelly.
All in all, Singer's practical ethics hits people's conventional ethical ideas. And it is of great importance for both theory and practice. First of all, it claims that animals should not be discriminated and they could also enjoy moral rights, because can also feel the joys and pains. Besides that, it helps to improve animals' social status, by means of changing people's minds. However, there are also some problems remained to be solved, such as its tendency to eugenics. Therefore, people should consider it with dialectical views.