When should we establish a general rule forbidding some act that is not by itself harmful? Or, basically the same thing, when is it wrong to do something that causes no direct harm by itself? Usually, there is no reason to forbid something that is not harmful. But there are cases in which the cumulative effects of people doing some thing would have harmful consequences even when the individual acts would not. One person electing to take things free from a supermarket does not really affect anything, but if no-one paid, there would be no reason for the shop to be there and provide those services. That simply would not work, and that’s basically why stealing even from a large collection of stuff is forbidden. (Of course, that’s also about rights of ownership, but I think they are ultimately based on a similar principle in the first place. In any case, I’m only examining this one particular line of thought in this particular post.)
But what’s the specific rule behind this? One might think it’s that a thing should be forbidden if it would have negative consequences if everyone relevantly involved (such as every customer) did that, but that cannot be the right answer. It would be absurd for it to be forbidden for anyone to draw money from their own bank account, even all the money there — but if everyone did that at once, there would be trouble. So what is the difference?
I have seen this question posed, without the answer I propose even being suggested, which is why I am writing down the answer here on the basis that it is something I have not seen said by anyone else yet. I haven’t studied this a lot and the answer is probably only partial. But anyway: It seems that the correct formulation for the rule for when to forbid something on the basis mentioned above is that An act should be forbidden if allowing everyone to perform it will lead to harm (that’s greater than the good gained from allowing it). People may withdraw all their money from the bank because letting them do so won’t cause everyone to do so. Apparently banks have closed their doors when there’s been some panic and everyone has rushed in to get all their money out. With shops, on the other hand, it is at least assumed that people won’t voluntarily pay enough for it to be possible to make paying voluntary.