Suppose a colleague tells you that another colleague, Sally, has submitted a paper to a conference in Rio de Janeiro and that she will be away for week. Further imagine that you know Sally better than the colleague who delivered the news. Knowing Sally well, you are fairly confident that if she were to go to Rio, she would stay longer than a week. You have inside knowledge about Sally that others do not have. Now suppose the colleague said the following to you:

“If Sally goes to Rio, then she will be away for a week”

And at a later date, you learn the following

Sally goes to Rio.

What do you conclude about her length of stay? According to your colleague and his knowledge about Sally, he thinks you will conclude, as he has, that Sally will be away for a week. However, according to your knowledge about Sally, you have to conclude that she will stay in Rio longer than a week because you know from conversations with her that she has always wanted to visit Rio and travel around the country of Brazil, and a week will certainly be too short of a stay for her to see it all. Hence, you conclude that she will be away longer than a week.