Why all these prejudices against a constant?
  The expansion of the observed universe appears to be accelerating. A simple
explanation of this phenomenon is provided by the non-vanishing of the
cosmological constant in the Einstein equations. Arguments are commonly
presented to the effect that this simple explanation is not viable or not
sufficient, and therefore we are facing the "great mystery" of the "nature of a
dark energy". We argue that these arguments are unconvincing, or ill-founded.
