• There are three kind of people: those who know how to count and those who don't.
  • There are two classes of people: those who think that mankind can be divided in two classes and those who doubt it.
  • There are 10 sorts of people: those who understand the binary notation and those who don't.

How many mathematicians do you need to change a light bulp?
None. Mathematicians can't change light bulps but they can prove that it is feasable.

How many researchers in analysis do you need to change a light bulp?
Three. One for the existence, one for the uniqueness and one to determine the initial conditions.

How many researchers in numerical analysis are necessary to change a light bulp?
3.9967 (after six itérations).

How many constructivists are necessary for the change a light bulp?
Impossible. They don't belive in infinitesimal rotations.

How does a bourbakist change a light bulp?
Light bulp changing is a special case of the more general problem concerning the maintenance of an electric system. In order to establish a lower and an upper bound of the number of persons necessary for such a task, we must check whether the conditions of lemma 2.1 (disponibility of the staff) and the conditions of corollarys 2.3.55 (staff's motivation) are fulfilled. Only in the case where all those conditions are fulfilled we can obtain the result by applying the theorem from section 3.11.23. We recall that the upper bound is to be taken in a measure space equipped with the weak-*-topology.