[idolaspecus]

I would definitely not say "Reasons and Persons" is clear. It might be precise (I personally don't think so, I think he makes tons of subtle mistakes), but it's at least not clear. It's full of ideas like "rational irrationality" which is at best a poor choice of naming, IMO.

[yesenadam]

> I think he makes tons of subtle mistakes

That's true of (at least) all important philosophy books, isn't it?

[idolaspecus]

Without context, sure, but when we're talking specifically about the precision of expression, I don't think so. Some philosophers operate closer to mathematical precision than others, and when those sorts of precision-oriented philosophers screw up their precision, it's a bigger problem. In Reasons and Persons, Parfit jumps through hoops to make his statements precise but ultimately trips all over himself (in my opinion).