It's explicitly forbidden in the Quran. Those who collect interest cannot stand before God and such. It was also forbidden by the law of Moses in the old testament. I'm not clear on when or how the Jews later managed to justify this practice. Islam still forbids it. Judaism and Christianity no longer do.  

 ‘fine print’ must be a universal constant 

 The Quran covers the subject thoroughly, but the Bible only contains a single verse mentioning it:

Exodus 22:25: "If thou lend money to any of my people that is poor by thee, thou shalt not be to him as an usurer, neither shalt thou lay upon him usury."

It's a pretty clear commandment though.  

 C'est vrai mais on vit dans notre monde actuel c'est très compliqué plein de paradoxes  au regard ce qu'on paie ou achète... dans un tel système construit sous des modèles d''usures.  Je me suis trouvée un jour avec un jeune cousin d'à peine 26ans qui a un excellent statut social, pas de soucis au niveau trajectoire pro et perso. De confession musulmane et pratiquant il  s'est retrouvé dans une crise psychotique du fait de ce  côté usurier du secteur banque assurance prêt immobilier il a fallu faire appel aux  pompiers pour une hospitalisation d'urgence, il  voulait abandonner son job, son bel appart dans l'un des endroits les plus chers dans Paris, sa voiture achetée dans les systèmes pas d'équerre dans ce domaine, promu à devenir chef de la grande société  d'assurance  à devenir chef de secteur,, il voulait tout vendre, abandonner rejetait ma tata et mon oncle en leur reprochant de ne pas lui avoir bien appris le Coran, ce juste  au retour de son voyage dans un pays musulmans..
Trop complexe à gérer pour une certaine génération qui n'a pas le recul nécessaire  

 Thousands of years ago and there were very advanced cultures in the American continent, it seems they dominated many things that in our era we still cannot understand well.

These great civilizations disappeared over time, I can't imagine how soon we will disappear. 

 I'm plainly in favor of contracts allowing compount interest between individuals. Interest is what best defines the value of money and the risk of not getting it back. If it's not expressed as a %%, consindering compounding over time, you have to model around that, essentially arriving at the same numbers or being less efficient.

Let's say you borrow me $100 and I owe you back $105 next year. How much do I owe you if I pay back early or late? Would you borrow me if I paid nothing for the favor? Etc. 

 I think it's the "charging for the risk" that is the problem. If they pay you back in full, the risk is non-existent. If they don't pay you back in full, charging extra does not remedy the situation.
 

 So Alice and Bob want to borrow money. Alice has a job and Bob would have a job if only I lent him some money to get to that work place.

Should I lend to Alice or to Bob? If Bob is offering me more in return, I would obt for Bob but for Alice otherwise. With Bob I might need more scrutiny to decide if I would facilitate getting to that job or if the money would not contribute to getting a job at all but for some extra return, it might be worth it.

I don't know, if you cannot account for risk in your lending business, I don't see much business. 

 I think the idea is that lending shouldn't be a business. 

 So lending should not extend beyond friends and family? Not sure if that's a good strategy for a society. I bet a society with lending beyond that small circle is more effective at allocating resources. 

 Why start with a false premise? 

 If there is no profit in lending, there will be less lending. Explain it to me where I got it wrong. 

 How does not making a profit relegate an activity "only to friends and family"?  

 Would you lend to strangers for free? Yes, some would but some would abuse that and resources would flow from gullible people to psychopaths. 

 The Old Testament says, paraphrasing, "only give a usurious loan to your enemy". The actual word used is "enemy", that's why the Jews don't loan each other with interest but the goyim are fair game. 

Now it is all we see. Finance is a %, and % is a shackle of debt slavery.  

 Creating money out of thin air?
Usury and leverage are bad things.
They only create debt for the poor and benefit of the few
 

 Yeah without interest people won’t lend.
Angle 1: Of course we aren’t really going to forbid people from offering loans with interest to people they would never otherwise lend to? Is that feasible? Is it good? I think no and no.

Angle 2: I think there is nothing wrong with an individual aesthetic of not lending with interest. Living in accordance with this aesthetic may even be a good thing. I wouldn’t lend to family with interest for example. I also like the idea of only giving to family, not lending. 

 medieval cristians were not against all lending. Templars lent to governments as a way to raise funds. Regine Pernaud tells about a Bishop intervening to expel from the  land a farmer who did not pay his debts. Generally proto-banks existed in small scale. Kings borrowed $ to go to war. BUT:

* coins were gold or silver. No inflation risk. You lend 10 coins, if you receive back 10 coins after 1 year, you have only lost oportunity cost. It is very different from lending 10 dolars to get 10 dolars back after 1 year - who knows how much the dollar will be worth then?

* oportunity cost was generally lower than today (slower and less diverse economy, smaller population, diffcult transportation, etc.) 

* there were acceptable rates, Pernaud again tells about 3% to 7% / year depending on where/who/when. 

And lenders charging more, (~10-15%) would be considered usurers. With some reason given the above points. 

Albeit... some agitation or even violent events against usurers (not only Jews) appear to have been instigated by people who borrowed and did not pay... 

in renassaince times all shame is lost... 1519 imperial election was a borrowing orgy.. the candidates were bribing the electors. And it was larger but not the first time electors were bribed. 
To expel the Dutch from Brazil in 1650, Portugal got indebted for generations...

 

 Thank you for sharing this, I don't know much about it I recently started looking into it. It's very interesting. 

 another point about the middle ages: 
precious metal  was relatively scarce (obviously, how much depends on where/when) and a good part of the economy worked on produce - tipically serfs would pay in produce. 

A village could have only a handful of coins - the coins would circulate among them - whoever did not have the 'token' at the moment would have to trade produce or services. 

Thus, lending and borrowing would happen among people who dealt with larger amounts  - lords, merchants, or maybe the eventual larger scale farmer - e.g., a serf married a serf heiress, then his son got a double sized farm, and so on, eventually he has to hire people. 
So, dont expect "Joe the smallest serf" borrowing often, even small quantities.