  The definition of negation has to be referred to the totality of a theory and
at last to what is defined as the organization of a scientific theory; in other
words, the definition of negation is of a structural kind, rather than of an
objective kind or a subjective kind. The paper starts by remarking that the
ancient Greek word for truth was aletheia, which is a double negation, i.e.
unveiling. Not before the 1968 the double negation law was re-evaluated, since
it was recognized that its failure represents more appropriately than the
failure of of excluded middle law the borderline between classical logic and
almost all non-classical kinds of logic. Moreover, the failure of this law is
easily recognized within a scientific text; this fact allows a new kind of
logical analysis of a text. As an example, the analysis of Kolmogorov 1932
paper shows that he reasoned according to arguments of non-classical logic
about the foundations of the intuitionist logic. The negation is defined as a
unary operation which, under the problem of deciding whether a doubly negated
proposition is equal to the corresponding affirmative proposition or not, leads
to a subdivision into classical logic and intuitionist logic.
