Reported is the construction of a primary mathematics curriculum on two kinds of data: the structure of mathematics itself, and the developmental realities of the child. Principles which have been assumed in this development are (1) since mathematics is abstract, the process of abstracting mathematics must be well prepared, (2) since mathematics deals with generalities, the variables involved in structures to be learned must be varied as much as possible to encourage generalization, (3) the necessity to take into account the difficulties in passing from the pre-operational to the operational stage. This involves a radical re-thinking of the way of presenting many classical parts of mathematics to young children, and (4) the need to follow the logical mathematical build-up of natural number and the other number systems in designing the curriculum. In view of these principles, the author stresses the necessity to teach relations and sets, accompanied by logic. (RP)