My goodness, is this all theoretical stuff, because it sure never will happen in real life.Is there something wrong with my contribution to this discussion? I am trying to respond with reason to your suggestion that there can be no free market without enforceable contracts.
I move out and spread far and wide your reputation for going back on your word. I take advantage of the numerous reputation-rating services that would crop up in a free market and let them know in detail just what you did. Next time you try to rent your house or enter any business transaction, you either must lower your price to lure a new partner or you may not be able to do business at all because you screwed up your reputation. This is why you would be very foolish indeed to act that way.
On the other hand, if you think that using the courts to enforce contracts is a nifty and efficient system, you must never have tried to do it. In your scenario, the owner of the house would tell you to leave and you would refuse. So he would turn off the lights and the water. Then he would change the locks. You would pay a lawyer to go to court to enforce the lease but in the meantime he sells the house. You get a judgement against him and he tells you to ram it. You got screwed anyway. The only difference is that in this scenario you wasted some money on a lawyer.
If the case an enforceable contract is made, the house owner can not remove the tenant if he wants to, the conditions for that would be in the contract, like not paying the rent or not taking care of the house or anything else mentioned. The tenant will be secure that he will not be evicted just like that. If a home owner switches of the lights or water enforcement of the contact becomes very important. The tenant probably started to build their lives around their 'shelter', maybe kids going to a school nearby, have a job etc. Why would protecting both the owner and the tenant according to the contract they both agreed upon not be desirable?
In business, would a business invest money when they can be be evicted whenever the realestate owner wishes. How about when business lease land, build a store and when everything starts to make a profit, the owner comes in and says, leave now? Sorry but all business, lease and rental will stop when enforcements of contracts is not available.
You have to keep in mind that not all people are trustworthy, and in my house rental example i even stated that the owner 'needed to sell the house or double the rent'. So even very trustworthy and honarable people can get in situation out of their control. Why would protecting your part of the contract not be desirable, even necessary to keep things honest. Because not everybody is your friend, family or neighbor you can trust. Most business takes place between total strangers.