Bookworm, you seem to be saying that an aircraft/airfoil combination with no wingtip vortices (consider the academic case of a perfect winglet) would have no induced drag. Or, an airfoil that stretched from one side of a windtunnel to the other (no wingtip vortices) has no induced drag. Am I understanding you correctly?
I didn't say "wingtip vortices" but "trailing vortex system" (or rather Barnes McCormick did). Vortices don't have to be shed at the tip. I have no idea what a "perfect winglet" might be -- if it's infinitely long then you might as well have an infinite span. As for windtunnels, there may be some practical effects that spoil the two-dimensional nature of the flow, but yes, perfect 2D flow means no induced drag. In a real wing of finite length, there must be vortices in order for there to be lift, hence there must be induced drag dependent on lift.