An axiomatization of interval scale measurement based on quaternary and dependent binary relations is presented for certain continuous sets of objects commonly encountered in psychophysics. The proposed initial assumptions appear highly suggestive and admit empirical checks. A sequence of propositions leads to the representation and uniqueness theorems in a direct and strict but rather undemanding way, as it is believed. Complete proofs are given for every step. They do not rely on concepts and results borrowed from alien branches of mathematics.