> If at the time of purchase I have full information about the product There's the problem. You assume full information is available up-front. In my opinion, a

> If at the time of purchase I have full information about the product There's the problem. You assume full information is available up-front. In my opinion, a return policy is actually the method by which the consumer obtains full information. Say I'm buying a TV. The interwebs will have all of the numerical information, and the showroom will have a demo playing on it, but that doesn't reflect the lighting conditions of my own home. Maybe there's an inaudible high-pitch noise that freaks out my cat. Maybe it gives me headaches after 4 hours, where my current TV doesn't do that until 6 hours. These are all examples of information that is relevant to my purchase decision, which is not available at purchase time. Thus, your hypothesis of full information is invalid. The easiest way to obtain this information, is through a trial period of some sort. A return policy is morally equivalent to a trial period, optimized for the most common use-case.