### Under the Big Dish

Well, we weren't quite

*under*it, but fairly close. Yes, me and two of the old gang which used to use this big dish got together for lunch to compare notes, and laugh, and discuss certain complexities, and the use of Subsidiarity.

They agreed that they would like to see it more widely used, and since they were buying, I scribbled an equation from the appendix of my book on Subsidiarity on a clean placemat, and said, the part you need is this. It's called Set Difference... but since you might not know about that, I will write it out longhand.

For two sets X and Y, we define the Set Difference X – Y in the following way:

X – Y = { z such that z is in X but z is NOT in Y }

Very simple.

Another way of doing it is to think of "subtraction" where there aren't any negative numbers, but just THINGS. Like this.

I have two boxes. One contains A, B, C, D.

The other contains A, B, D, E.

When I subtract the second from the first, I get C, which is in the first box but not the second box. Very nice. Lots of fun. Computers like doing this sort of Boolean thing, it makes them feel wanted and useful.

Now, in order to do Subsidiarity, you need a little more than that, but until the book comes out, you can see the introduction here.

I strongly advise that you get the book. No, all the set theory is in an appendix. The rest has Chesterton and interesting stories and stuff about Aquinas and cable TV and lines from the Bible... lots of fun.

And yes, I rather expect that my friends will want several copies for their co-workers... it will do them so much good.

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