We can think of a monetary system without banknotes or coins, where people would

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We can think of a monetary system without banknotes or coins, where people would only have their money in banks, using it with credit cards and the like. Of course, there would be nothing in banks except for information on the amount of money each person would have. Now, I think that in this system there would exist nothing of which we could say "That is one euro" or "one dollar" (or whatever). But still it would be true that some people would have, say, one million dollars. My question is: if there is nothing which is one dollar, how can somebody have one dollar or a million dollars?