OK. The vocative requires lenition on consonants that can take a séimhu. What about proper nouns that begin with vowels? My gut tells me that they don't lenite but I'm not sure.

Mar sampla: when writing a letter to a priest how would one begin?

A Athair???

I know I'm going to feel really dumb for asking this later but I can't find it addressed in any of the books I have with me.

Go raibh mile maith agaibh.

Le meas,

James

My gut tells me they lenite, but in fact they do not.

I meant that vowels do not prefix an 'h' after the vocative particle "a".