Social cost was in many ways a reaction to pugo. The so called pagovian tax, which is that when you have a negative externality, you should impose a tax on the apparent perpetrator. And i think what cost would have said, and maybe he said it, ah, and think probably mentioned on this programme, is that that's one way to solve it. It may not be the best way. But cose understood that the real world has complexities in it that most economists overlook when they do their theories. So kind of acted ligt o, sir. That might be cheaper than foregoing an output, which the tax will produce. Cos said basically, look,