Active Galactic Nuclei and Quasars: Why Still a Puzzle after 50 years?
  The first part of this article is a historical and physical introduction to
quasars and their close cousins, called Active Galactic Nuclei (AGN). In the
second part, I argue that our progress in understanding them has been
unsatisfactory and in fact somewhat illusory since their discovery fifty years
ago, and that much of the reason is a pervasive lack of critical thinking in
the research community. It would be very surprising if other fields do not
suffer similar failings.
