Let me say this straight. If your sole goal is to learn about probability applications you won’t need this chapter at all, so you are permitted to skip the coming lengthy digression. Before jumping to this conclusion, however, consider the following. Like myself, you have probably spent some time as a budding physicist speculating about the dramatic revolution in our perception of reality that the quantum revolution has brought about: we have to accept that God does play dice. Do you think we can really hope to figure out the rules of this game of (weird, and perhaps loaded) dice without trying to understand what we mean by “probability”?