"Well, I say I recognize more than you. I recognize that, the option to buy a sandwich at a location for a particular price is a public good."

Why is it a public good?

"I say the option to walk into a bookstore and browse books, and walk out, without paying, is a public good. You get something for free, and it's quite difficult for the store to give different treatment to people who plan to buy something, and people who don't. And the fact is that this public good exists."

As I have said before in a different post, a chance of customers spending money, is in fact money in the bank to a business with a large enough volume of customers. A 50% chance of getting 100 dollars is worth something to most businesses, so they will spend some money to get that money.

Ask yourself whether you would be willing to pay a certain amount of money to have a 50% chance of getting 100 dollars. Most people would be willing to spend something (usually less than 50 dollars) to buy that deal. Again, most people would be willing to pay SOMETHING to buy a "chance", even if it is not a guarantee of money, but a "chance" for money.

Because people will spend money to buy a "chance", a chance at winning money is worth something to the people who will spend for it.

Borders is implicitly giving customers money, by giving customers a comfortable chair and reading materials. And yes, the customer is paying for it, because the customer is giving back something very valuable to Borders: A "chance" that he will buy something. And remember, chances are valuable, so the owners of Borders are willing to spend money (provide seating) to buy the valuable chance that a customer might buy a book.

So when the owners of Borders provides seating to the public, they are not usually providing a public good, though the charitable giving of the company certainly would qualify.

"Public good problems are solved all the time, without force."

Yes. The culture does encourage people to be generous with each other, and so many (even most) public good problems are solved that way. But for some public good problems, there is no known efficient way of solving the problem. The overwhelming majority of people will vote for a publically owned defense force (a public good), enforced by taxation for example, to prevent our country from being annihilated. (It is simply too inefficient not to have a publically owned military!)