We could always believe that there is no internal clock inside us. However, it would be audacious to respond no to the question that is opening this chapter, considering that one may even argue that there are several internal clocks. That said, we know that we are able, for instance, to synchronize actions and make accurate judgments about time. As well, if a traffic light delays turning from red to green, it will not have been necessary to begin an explicit timing activity to have, at some moment, the intuition that there is a delay. This intuition, this impression of delay, necessarily has to be the fruit of a mechanism allowing some measurement of time.