The basis of a rigorous formal axiomatization of quantum mechanics is const
ructed, built upon Dirac's bra-ket notation. The system is three-sorted, wi
th separate variables for scalars, vectors and operators. First-order quant
ification over all three types of variable is permitted. Economy in the axi
oms is effected by, e.g. assigning a single logical function * to function
(i) a scalar into its complex conjugate, (ii) a ket vector into a bra a a b
ra into a ket, (iii) an operator into its adjoint. The system is accompanie
d by a formal semantics. Further papers will deal with vector subspaces and
projection operators, operators with continuous spectra, tensor products,
observables, and quantum mechanical probabilities.