  We consider a hypothetical bound state of two electrons even if we leave the
binding mechanism unknown. The bound electron pairs should behave as bosons and
we conclude that the paired electrons are 'apparently' in the highest energy
states of all the occupied states. We call this multi-particle state an
'apparent' Fermi surface. Then the solid in concern must be a type 2
superconductor for a charged boson fluid is theoretically known to be as such.
Moreover the Bose-Einstein condensation is known to be closely related to the
critical temperatures of high Tc superconductors, which is consistent with our
model. Most notably the model may describe a superconductor either with or
without a Fermi surface. We propose two experimental methods to detect a bound
electron pair, low energy electron-electron scattering and photoemission from
high Tc superconductors.
