Three of the traditional quantum axioms (orthocomplementation,
orthomodularity and the covering law) show incompatibilities with two products
introduced by Aerts for the description of joint entities. Inspired by Soler's
theorem and Holland's AUG axiom, we propose a property of 'plane transitivity',
which also characterizes classical Hilbert spaces among infinite dimensional
orthomodular spaces, as a possible partial substitute for the 'defective'
axioms.Comment: 5 pages, 0 figure
