However many things we may have done, we are yet to a certain degree fresh for that which we are going to begin. Who, on the contrary, would not be stupified if he were to listen to the same teacher of any art, whatever it might be, through the whole day? But by change a person will be recruited, as is the case with respect to food, by varieties of which the stomach is re-invigorated and is fed with several sorts less unsatisfactorily than with one.