Are you referring to your position that banks, by allowing withdrawal of depositors' money on demand, implicitly claim not to lend any of it out?
I don't find that position convincing either, and I can't figure out why you hold it.
Almost always, relatively few depositors want to withdraw their money simultaneously. Therefore, it is possible for banks to lend out most of the money deposited with them and still, almost always, to allow withdrawal by any depositor who in fact wants to withdraw his money. Since it's possible to do both---it is obviously possible, because banks do so---how is doing one an implicit claim that the other isn't done?
But, never mind implicit claims. What if a bank were completely explicit about what it does? What if it had a big sign in the window, like this:We lend out most of the money deposited with us. This means that if too many depositors should happen to want to withdraw their money simultaneously, they won't be able to. If you don't like this, don't deposit your money with us.
Would that be acceptable to you? Would you consider such a bank to be acting in any way fraudulently?
Yes, I would. Since the promise to redeem a demand deposit cannot be guaranteed by any bank, and since the system introduces a degree of instability which while uncommon, when realized is catastrophic, the practice should be outlawed. Even if the bank makes it explicit in such a way as that everyone understands, it should be outlawed. There are some instances in law where contracts are not binding. People cannot contract themselves into indentured servitude for good reason. The simple solution for banks is to use 100% reserve demand deposits, and simply sell time deposits for customers who want to take on more risk.
The system only works as it does because money is fungible. If you ran a public storage company and operated the same way because you can get away with it most of the time, then you would go to jail for fraud.
There are other questionable legal practices which are examples of logical contradictions besides fractional reserve banking. Take the practice of short selling. How is it that one can legally sell something that they don't have title to, but is in fact borrowed? You wouldn't let someone borrow your car with the intent to sell it, because cars are not fungible. Why should the practice be any different with stock shares that are fungible? If I had knowledge that a recall was going to be issued on your car before most everyone else, I then borrowed your car and sold it on the used car market with the anticipation that I could buy a similar car back at a much cheaper price, I would go to jail for fraud.
Simply making these things legal because some form of consent is granted either implicitly or explicitly doesn't change the fact that they're morally wrong, and destabilizing.