A constructive proof of Tarski's undefinability theorem and Gödel's incompleteness theorems

The paper presents a fundamentally new constructive proof of Tarski's theorem on the undefinability of truth and Gödel's incompleteness theorems, based on the inexpressibility, by purely formal means, of the existential content of a theory (the "ostension deficit"), without which formalism loses its meaning. It is shown why the classical Gödel theorem arises from the same reason.