  We investigate the following problem: For what $f$ and $g$ is the commutator
$i[f(P),g(Q)]$ positive when $f$ and $g$ are bounded measurable functions? This
problem originated in work of James Howland and was pursued by Tosio Kato who
suggested what might be the answer. So far there is no proof that Kato was
correct but in this paper we discuss the problem and give some partial answers
to the above question.
