In Earthlings the idea is exposed that if other animals suffer there is no reason to justify not having that suffering in mind in the same way as the suffering of other humans.
Since all animals inhabit the Earth, we can all be equally considered as inhabitants of the Earth, that is, earthlings. There is no sexism, racism or speciesism in the term "earthling" because it embraces each and every one of us, hot or cold blood, mammal, invertebrate, bird, reptile, amphibian, fish or human.
Humans are not the only sinful beings on this planet. We share the world with millions of other animals that have their own conscience and interests. However, we try to dominate other animals and treat them as mere objects that exist for our benefit. This is due to the prejudice of speciesism. By analogy with sexism or racism, the term speciesism is a prejudice or favorable attitude toward the interests of individuals of the same species and against individuals of other species.
This is what Peter Singer explains:
"The racist violates the principle of equality by giving greater weight to the interests of members of their own race when there is a confrontation between their interests and those of another race. The sexist violates the same principle by favoring the interests of his own sex. In a similar way, the speciesist allows the interests of its own species to predominate over the essential interests of the members of other species. The model is identical in all three cases. "
Although the most correct thing would be to say that speciesism does not give the same value or consideration to the interests of other animals for the mere fact of being of another species. Or it simply does not give them any value or consideration. It is not necessary that there is a conflict or confrontation between individuals. The exploitation of other animals is not caused by the conflict but only by the benefit we obtain from it. It is important to point out that speciesism is not applicable to living beings in general but only to sentient beings, since plants can not feel pain, nor feel anything in general, since they have no nervous system and for this reason they lack interests. If a being feels, then there is no justification for not considering him as an individual who deserves respect for himself. It does not matter the species of the individual. The principle of equality requires that the inherent value of everyone be valued in the same way as the inherent value of any other.
The first fundamental step for us to solve this serious problem is to understand that all sentient beings deserve consideration as persons and, therefore, not be used as mere means for anyone's purposes. The first step is veganism.