[sverhagen]

If they'd have turned the corner to see the engine fall out from underneath the car, while you'd have already strolled off the scene with the money, they suddenly wouldn't be so happy with finality. I think finality in transactions is more something about "the nominal case". If I'm a transaction processor with significant volume, I would like to reach some final state without too much intervention, but I can still handle the exceedingly-rare exceptions with (expensive) humans. Where that point lies differs per application, also dependent on what kind of service I'm wanting to deliver.

[rlpb]

> If they'd have turned the corner to see the engine fall out from underneath the car, while you'd have already strolled off the scene with the money, they suddenly wouldn't be so happy with finality.

Maybe, but since I also wouldn't be too happy if they reversed the transaction after taking the car, we both agree in advance that the sale will not be reversible. For the payment, that's done by using cash (and the possession of it), and for the car, also just possession. I give the buyer the opportunity to inspect the car before committing to the sale, and then it is "sold as seen". Unless I committed fraud, the engine falling out from underneath the car will be the buyer's problem, including in law.

It is always possible to seek redress through the courts whether the financial transaction itself was reversible or not, so that's not relevant here. Neither is the fact that to do that knowledge of identity and evidence is required; those concerns also exist regardless of transaction reversibility.

[jacquesm]

That's why you test-drive a car and/or have it inspected. If it is a clunker and the price of the inspection approaches the price of the car you can just take the risk. In any other case an hours worth of time of a competent mechanic will tell you all you need to know. After that the risk is yours if you decide to go through with the purchase. If something does turn up that wasn't disclosed the seller will usually be happy to adjust the price. And if not you are only out the inspection fee. Typically $50 to $150 so well worth it on any vehicle purchase that is in the price range where 'engine fell out' feels like it isn't on the menu of expected events.

[kube-system]

> If they'd have turned the corner to see the engine fall out from underneath the car, while you'd have already strolled off the scene with the money, they suddenly wouldn't be so happy with finality.

Which is exactly the point of the finality of the transaction. Private party car sales in the US typically are not warranted. The risk of maintenance on a used car is non-zero, and the buyer accepts this risk when buying a vehicle with no warranty.