Part of the rationale for the patent system is that it is supposed to encourage people to disclose trade secrets that they would not otherwise disclose. Howeve

Part of the rationale for the patent system is that it is supposed to encourage people to disclose trade secrets that they would not otherwise disclose. However, if you can tell how a thing works just by looking at it, then according to that rationale there is no point in allowing such an invention to be patented (at least not on that basis). Unfortunately, that does not seem to prevent many completely obvious things from being patented (e.g. one click shopping).