Quote: DaveO "So how come the money supply increases as a result of all this?'"
Well because multiple people 'have' the same money.
Quote: DaveO "The drain on the money supply occurs when the money lent is not deposited or if in some way it is returned iti the central bank.'"
A deposit and loan are the same thing just viewed from a different perspective. When you deposit money in your bank account you are loaning that money to the bank. When a bank makes a loan they are depositing that money with you.
Quote: DaveO "Interest is not special. It just requires money. The question is where does that money originate from?'"
It requires money just as the mark-up in a shop requires money. This again doesn't require new money, it is simply money circulating through the economy funding economic activity. So the shop owner borrows money to buy stock. He adds a mark up to the cost of the stock that covers his costs and his profit. Part of his costs are the cost of borrowing the money. When he sells the stock he pays the interest on the loan. The bank then has its profit which it puts back into the economy via another loan, the money markets, dividends etc.
Quote: DaveO "And? Yes you would just be renting their safe. That is what kind of what full reserve banking means which is similar to what you describe.'"
And you'd have a massive decrease in economic activity as deposited money will just be sat there losing value. We are currently seeing the effects of banks having to maintain larger reserves and restricting lending. This has reduced the money supply.
The massive (and unprecedented) progress made over the last 20/30 has been funded by the financial industry. Moving money efficiently around the world to where it can be used most productively. This is pretty much the purpose of investment banks.