Singer argues that if one accepts utilitarianism, then one must also accept vegetarianism. Basically, if you accept that pain is morally bad, then eating meat is bad on the grounds that is causes pain to animals.
1. If Utilitarianism is true, then pain and pleasure are the basis of all moral value.
2. Animals experience pleasure and pain.
3. If pleasure and pain are the basis of all moral value, then animals are morally significant.
4. So, if utilitarianism is true, then animals are morally significant.