Thinking about this and defining "value" as "what people want" (i.e. "wealth" in the essay), it seems to me that every freely-entered-into transaction must increase overall value. [Since the two exchanged items must be valued more by their final owners than their initial owners, otherwise the transaction would not occur.] This seems intuitively sensible to me and suggests that trade is a good thing :-)

However, this then leads to some, to me, unintuitive conclusions:

1 - "value" can disappear very rapidly. (I valued an ice cream more than £1, bought it (total value in the world goes up), then ate it (total value in the world goes down)). Also, simply becoming disillusioned with something destroys value (I value it less).

2 - the advertising and marketing industries create a lot of "value", by making people want more. (Yesterday I would only valued a new pair of shoes by brand X at £20. Today I saw an ad which made me covet them. I now value them at £100. If I find them for sale at £40 I will buy them and be very pleased.)

I've not studied economics, is this definition of fairly ephemeral and manipulatable "value" meaningful?