I'm not much of a Hobbes fan at all. But I do like one move he makes, even though I don't think he manages to do it quite adequately. One of Hobbes's concepts is that of personation. For X to personate Y is for X to represent Y as the source responsible for Y's words and deeds. I think Hobbes is quite right that we need a concept like this to understand personhood properly. It is needed to understand one facet of real personhood; and it is needed to understand legal fictions like corporate personhood.
Just about anything can be personated. The most important form of personation (from Hobbes's perspective) is representation in a person. If a group of us is adequately represented by one person, that person personates the whole group as one person by being the representative in virtue of whom the whole group has a unified responsibility. Likewise, if we allow groups to be personated under law (as we certainly do), we are allowing the treatment of an entire group as a single person, for at least certain purposes.
There are other cases of personation, though. One important one is when one person personates another. Thus (Hobbes's own example) Moses personated God by his ministry; that is, in the way he interacted with God, Moses represented God as an agent responsible for words and deeds. Another important one is when a person personates himself -- which we all do when we treat ourselves as agents responsible for our own words and actions.
Where Hobbes goes wrong, I think, is in thinking that personhood just is personation. This leads him to the odd view that every personation is a different person. This means that the same person (in our sense) can be many different persons (because he or she can be personated by many different people). This comes out in Hobbes's explication of the Trinity: the Father is God personated by Moses, the Son is God personated by Jesus, the Holy Spirit is God personated by the Apostles. Hobbes himself later backed off from this. Taken strictly it isn't actually heterodox -- the Father is personated by Moses, the Son is personated by Jesus, and the Spirit is personated by the Apostles -- but (1) they don't each personate just one person; (2) it isn't because of Moses, Jesus, and Peter that there are three persons in God. And even though we can read Hobbes's formulation in a non-Sabellian way, it doesn't have anything in it to prevent a Sabellian reading. So Hobbes's account of personhood as a being-personated doesn't do one of the things he originally thought it could, namely, provide a complete account of the orthodox doctrine of the Trinity.
It's not surprising, though; Hobbes's account fails as an account of human personhood as well. For one thing, nothing in Hobbes's account privileges one form of personation over another. (This is one reason why Locke's account of personhood as 'forensic', although very similar, is superior to Hobbes's: Locke privileges divine forensics, i.e., divine personation, over other kinds, followed by self-personation.) For another, personation is probably not the best foundation for an account of personhood, despite the fact that any complete account of personhood needs to say something about personation. An account of personhood should not allow things arbitrarily to be designated persons in the proper sense, because we can't really think of persons in that way (morally, politically, or metaphysically). There needs to be a standard against which the propriety of a personation can be measured -- and that standard will necessarily be a better foundation for an account of personhood than personation itself will.
