here is an example. you have a lamp that's turned off. after 1 minute you turn it on, then half a minute later you turn it off, then a quarter minute later you turn it on, and you keep halfing the amount of time you take before you flip the switch, and after 2 minutes passes, you will have completed an infinite amount of switching the lamps switch. the question is, will the lamp be on or off in the end, because it can only be either on or off.