There is a very long and learned discussion in Roman law about the following question. Can you make various kinds of stipulations subject to conditions? And if so, what are the conditions that are permissible and which are not? And so, for example, to take a perfectly innocuous condition, what you can say is, "If it turns out that X dies, I hereby agree to pay you a 1,000 sesterces," and that's, of course, just a contract of insurance written on the life of the person who happens to die. And the reason why you want to make it conditional is that if you've paid a premium in a separate transaction, the last thing you want to do is to say that the money is never owed or is always owed. You're making a bet on the life of this person, and what the condition does is allows you to make the obligation work under these kinds of circumstances. But sometimes, the Romans get themselves a bit more speculative. And so one of the things that you would start to say is, "Can you make a promise on the sense that I will pay you 1,000 sesterces if it turns out a hippopotamus learns how to fly." And there you start looking at that promise and say, "What are you talking about under these cases? What's going on?" And so that becomes kind of an academic sort of question, but it becomes fairly important in the following case: What happens if it turns out that you do this in a contract on the one hand, or you do it in a will on the other hand? And it turns out that what Gaius says is the general rule is that we regard the thing as unenforceable because of the impossible condition And he said, "The rule turns out to be good with respect to contracts, but not with respect to wills." You cannot expect the heir or the beneficiaries under the will to follow the whim of somebody else. And so therefore what you do is you void the condition under those circumstances, instead of voiding the obligation, on the grounds that he purported to do something, and it's beyond his power to correct the overall situation. If you go forward in both Roman law and an Anglo-American law, where these obligations now are allowed to descend, what you often discover is very strange things start to happen when it turns out that there's a promise made by a given person, who then turns out to die. And now the heir decides not to honor it. And what it is is it goes extensively to consideration and all sorts of bargained arrangements. Under the Anglo-American law, if there's no consideration for a particular promise, then the thing is not enforceable. Roman law does not have that as a universal principle, but the common law does. And so what you do is in the most famous case called Williams and McGowan. You have a situation where somebody is standing on the ground, his employer is up top, and a log starts to fall on his head. And the poor employee rides this thing down, saves the master, who then promises to pay him $10 a month for the rest of his life. And then he dies and his estate refuses to pay the money. You can see what the risk is. So they now go around, they're just enraged about this because they understand what the intention is, and they don't think that this was a bargain because the so-called consideration was passed. Everything that was supposed to be done lay in the past, not in the future, and so therefore it's not a bargain but it's a gift conditional upon something happening, which is gift meritorious. Romans would have very little problem in enforcing this promise, and so what the American angle, American law does is it starts to invent other exceptions to the consideration doctrine in order to let this thing go. And this is a lesson that every lawyer has to understand: is whenever you negotiate a contract with X, it turns out that the assignment risk and the post-mortem risk is always there. The moment you change the nature of the person who's the obligor, you change the nature of the particular risk in question