  It is sometimes argued that the unattainability of zero temperature is a
consequence of the second law of thermodynamics. Historically, the independence
of the unattainability of zero temperature from the second law was proven more
than 80 years ago, yet this assertion was repeated in the literature. This
assertion naturally leads to a doubt that the unattainability of zero
temperature is not equivalent to the Nernst heat theorem. The apparent
contradiction between the Nernst heat theorem and residual entropy further
complicates the problems of the third law. Totally, the validity of the third
law seems to lose, giving an impression of somewhat ambiguous hypothesis to it.
The author has recently settled the apparent contradiction between residual
entropy and the Nernst heat theorem by refining the statement of the third law.
Based on this refinement, two controversial problems, the independence of the
unattainability of zero temperature from the second law and the equivalence of
the unattainability with the Nernst heat theorem, have been solved.
