Is everyone equal?

It's a fundamental tenant of modern liberal societies that all humanity is equal in some major sense of the word. Perhaps this means that their lives are of equal worth etc. Obviously people are different when it comes to things like intellectual ability, physical ability, physical morphology, and psychological profile and disposition. These are clearly not up for debate. But the law and traditional morality has always considered one life as equal to another in some set of moral senses.

However, in this post I'd like to question this assumption. What can these qualities be? Some ineffable sense of humanity which everyone has in mere virtue of their humanity? This is not plausible for aliens or artificially created conscious beings may lack humanity yet their lives have all the value of humans lives. So that suggestion of some nebulous "humanity" which all humans have and makes it so that all of us are equal seems dubious. For whatever quality one may have, it may vary between people. With regard to virtues and vices, people are different like anything else. Think about animals. Must liberal egalitarians maintain that animals are not equal to humans in basic worth; that a human's life is worth more, that it is a bigger tragedy for a human to die or to suffer than an animal. I suspect that even most animal rights activists believe this. Given the choice to between an arbitrary human being and an arbitrary cat or lobster to avoid some great harm but not both, most animal rights activist will choose the human to avoid the harm. Human lives are simply worth more they will say which isn't to say that non human animal lives are worth nothing. Now people probably think this because humans have more capabilities more potential or have richer mental lives than other creatures. Thus they reason, human rights are more important. Human lives are more important. Human suffering etc. Of course this is not always the case; some intelligent animals such as great apes and dolphins and elephants probably have more capabilities and richer inner mental lives than severely retarded people.

However, if the value of a life is dependent on these factors (capabilities, richness of mental lives, etc) and not some intangible "humanity" then human beings individually vary in these qualities from one person to the next just as humanity vary from other species though in smaller degrees. So it seems that at least somewhat plausibly that human lives can vary in their basic value with some lives worth more. This seems more plausible to me given certain examples. Surely the lives of moral saints are worth more than Nazis? Gandhi's life, his suffering, his basic well-being is of more concern than Hitlers is it not?

However, though this may be all well and true, it doesn't mean that the law ought to respect it for practical concerns. Because it is too difficult to judge the worth of lives, the law may nbot be the right place to adjudicate and all lives ought by the law to weigh all human lives equally. Things like organ donation, allocation of health, economic and other resources ought to follow the egalitarian basic rule of thumb despite acknowledging that it is morally false.