Full Idea
I cannot answer the question 'What ought I to do?' until I have answered the question 'Who am I?', and any answer to this question will specify my place in a nexus of social relationships.
Gist of Idea
My duties depend on my identity, which depends on my social relations
Source
Alasdair MacIntyre (A Short History of Ethics [1967], Ch.13)
Book Reference
MacIntyre,Alasdair: 'A Short History of Ethics' [Routledge 1967], p.187
A Reaction
This is the beginning of the modern critique of deontological ethics coming from revived virtue theory. As it stands, MacIntyre's idea sounds contractual, but I think he intends it in a more organic way. I am a fan.