"Usury" is still a word in use but now, for legal purposes, it means "interest that a lender charges a borrower at a rate above the lawful ceiling on such charges" rather than just any interest at all.
traditional usage of usury was the same, any interest charges at a rate above the lawful ceiling, just where the ceiling was 0% for christians and in a like manner for moslems.
In the Islamic finance model Muslims lending to Muslims, you don't charge interest so much as take a position in an investment with an eye to future value. At least that's how I understand it. There can still be a lein over assets, and a tail of payments and the final state would put both lender and debtor "where they expected to be" under the contract.
Between Christians and Muslims, Christians and Jews, Jews and Muslims different rules may/may-have applied.
Kings (of england, and other places) valued Jews precisely because of the fluidity of their lending to the crown at interest under catholic proscription regarding loans between christians, not the least because at long term consequences in access to jewish loans you could repudiate the debt and (or encourage your citizens to) conduct a pogrom.
That's a strange way to phrase things. It's a bit like saying that the Church recognizes the licitness of murder under a lawful ceiling, but that this ceiling just happens to be 0 per year.
Interest as such is recognized as theft and therefore an injustice.
Well murder is similar in that it means an illegal or immoral killing. There are times (say in self defence) where it has taunt it is moral and should be legal to kill, because that isn't murder. So similar to this, it changed usury to illegal lending rather than lending.
As you point out, the difference between money and the tooth fairy is between their characteristics and rules. Economic theory then focuses on money, the economy, and their characteristics and rules to develop insights into patterns, behavior, and previously unseen characteristics inherent to economic theory.
Anyone is free to create a theory of tooth fairies and attempt to find similar relevance.
Between Christians and Muslims, Christians and Jews, Jews and Muslims different rules may/may-have applied.
Kings (of england, and other places) valued Jews precisely because of the fluidity of their lending to the crown at interest under catholic proscription regarding loans between christians, not the least because at long term consequences in access to jewish loans you could repudiate the debt and (or encourage your citizens to) conduct a pogrom.
Interest as such is recognized as theft and therefore an injustice.
By that reasoning, there's no such thing as "chess theory" either.
> with the end of scarcity
Scarcity ended? Nobody told me!