Full Idea
Carnap's ultimate ambition in the Aufbau is to provide a constitution-system within which any predicate of any scientific vocabulary can be explicitly defined in terms of primitive relations holding among basic elements, using type theory.
Gist of Idea
Carnap tried to define all scientific predicates in terms of primitive relations, using type theory
Source
report of Rudolph Carnap (The Logical Structure of the World (Aufbau) [1928]) by Tim Button - The Limits of Reason 05.2
Book Reference
Button,Tim: 'The Limits of Realism' [OUP 2013], p.35
A Reaction
David Chalmers has a modern shot at the same project in 'Constructing the World'. Ramsey sentences seem to be part of the same game.