2. The standard theoretical statement that the lengths of the hypotenuse c and of the leg a (in other words, the lengths of the diagonal and of the side of the square) are incommensurable quantities should be replaced by the following correct statement: the theoretical proposition of the existence of incommensurable segments contradicts to the practice (i.e., construction); incommensurability of segments is a mathematical fiction, the consequence of violations of the logical law of identity of forms and the law of lack of contradiction.