The aim of this essay is to analyze the concept of acquaintance in the philosophy of Bertrand Russell. First, Russell’s epistemological program and works are presented in a general manner. Then, the concept of acquaintance is defined and characterized, as well as the so-called principle of acquaintance. After that, acquaintance is placed in Russell’s epistemology as the core of his theory of knowledge. Finally, I will make some critical remarks concerning the role of acquaintance in Russell’s epistemological framework.

For Tarski talk about the truth in a language, and not generate contradictions, it requires doing it from a different language with greater expressive power: the metalanguage. So, a metalanguage is a language that is used to talk about another language. In scientific language this distinction is very important. In physics, the notion of symmetry is shown through the language used within physical theories. In this way, through algebraic language ─automorphism─ we shown the symmetry ─invariancia, order, equilibrium─ finding (within the (...) language of these theories) the use of the notion sometimes as a principle and sometimes as argument. The distinction in use of the notion of symmetry, on the part of physics, allows us to glimpse symmetry as a term of the metalanguage. Through a brief historical reconstruction ─from the Greeks to present time─ we show the notion of symmetry as a metalanguage term distinguishing the use ─principle and argument─ that physics makes of the concept. (shrink)