Arbitrary partiality

[This appeared on my old blog]

"We should all agree that each of us is bound to show kindness to his parents and spouse and children, and to other kinsmen in a less degree: and to those who have rendered services to him, and any others whom he may have admitted to his intimacy and called friends: and to neighbours and to fellow-countrymen more than others: and perhaps we may say to those of our own race more than to black or yellow men, and generally to human beings in proportion to their affinity to ourselves."
(Sidgwick's The Methods of Ethics, Book 3, Chapter 4, Section 3)

Many people endorse partiality; the idea that we have special obligations towards some groups of people - such as towards your family, or to your country. But do we have an obligation of partiality towards anyone you share any kind of affinity to, no matter how arbitrary? Do I have special obligations to all bloggers? To philosophy bloggers? To people called Al? To people of my race?

I see it as difficult to justify partiality, due to the very simple thought that there's something unfair about favouring people to whom you happen to have some personal connection.

But with the above in mind, I also tend to think that it's difficult to justify partiality because any justification must be careful not to establish too much.