The rule is an hypothesis about the four cards. These cards represent the world that we are trying to analyze, and the reality that we are trying to understand when testing our hypothesis.

Let us read the rule carefully while trying to make an effort to understand exactly what it is telling us. It is a general rule: in order for it to be true, all the cards with a vowel on one face must have an even number on the other.

If we could turn over all of the cards, it would not be hard to establish whether the rule is true or false. However, we are only allowed to turn over a maximum of two cards. When you think about it, this task reproduces the situation in which we normally find ourselves when we try to understand something(of/about reality around us). We hardly ever have all the information and we must try to reach a conclusion and understand the situation only by using the information available. In medicine things also work like this: we can never have all the information needed to make a diagnosis or a prognosis or in order to decide on a therapy. We must reason on the basis of the available elements.