The distribution function for fermions has been derived from collision
theory by using the detailed balance hypothesis. Its form f(epsilon)
= {exp[beta(epsilon - mu)] + 1 - 2/n2}-1 goes to the correct boson (n
= 1) and fermion = infinity) limits. Further the equations for the den
sity matrix have been derived from the Hamiltonian. The zero order app
roximation gives a distribution having the same form as that derived b
y the detailed balance arguments.