The subject of the book is a descent into the depth and the intelligence of the language, especially of natural language. And it is also the suggestion of an explanation of an aspect of natural intelligence that seems to consist of an appropriate use of the logical contradiction. But nothing about all this could exist if "the negation" did not exist, as the book will gradually try to explain. We speak of paradoxes but this is just to show the intelligence of the language that, through a paradox, points out an abuse of the language and of cognitive discard. This last one could be defined as the unknown background of every language. So we also speak of general rules for a correct use of the language, those which are above the merely grammatical rules. As a matter of fact a sentence which is grammatically correct can equally be an abuse of the language.