  An introduction to the physical interpretation of the Coulomb logarithm is
given with particular emphasis on the quantum-mechanical corrections that are
required at high temperatures. Excerpts from the literature are used to
emphasize the historical understanding of the topic, which emerged more than a
half-century ago. Several misinterpretations are noted. Quantum-mechanical
effects are related to diffraction by scales of the order of the Debye
screening length; they are not due to quantum uncertainty related to the much
smaller distance of closest approach.
