Capital is stuff people want. It's a warehouse full of couches, or a truck full of iPads. Or, on a desert island, a pile of hand-carved tools. We can trade this "stuff people want" for "stuff we want."

Over time, we've developed abstractions called "dollar bills" that represent stuff people want. This allows me to have a more general form of capital--instead of having to exchange my "stuff people want" for what I want, I simply exchange it for money, and then trade that for what I want. This makes trade much easier--I don't have to find someone who wants 1,000 iPads in exchange for a piece of industrial equipment.

But I repeat--this is just an abstraction. To create $1 or $1,000 or $1,000,000 of capital, resources must first be used to produce things that people want.

Now, in our modern society, there are all sorts of ways to get ahold of these abstractions. Some people work for them. Some people are given them by family members. Some people make bets--at casinos, at horse races, or on the stock market--and win. So it is certainly possible to point at a given possessor of capital and say--"look! he has capital, but has not produced things that people want!" But that's the nature of people who own capital, not of capital itself.