I am 100% certain that it is impossible to make half a sandwich. That's not to say it's impossible to have or eat half a sandwich, only that it's impossible to make one. If you ordinarily make a sandwich using two slices of bread and you decide to make one using only one slice of bread folded over, it may be a half-sized sandwich, but it's not half a sandwich. To get half a sandwich, you have to make a whole sandwich and cut it in half.    It's the law.