The article argues the application of the diary as a method that allowed the establishment of the genesis of two fundamental mental actions, affirmation and negation, which, being expressed initially by non-verbal means (movements, facial expressions, vocalizations, emotions, etc.), then by a series of laconic preverbal and verbal means (yes and no), play an essential and decisive role in human life and activity. The process of birth and evolutionary development of affirmation and negation is presented in the current chronological journal through scientific observations and empirical evidence for almost two years based on longitudinally recorded data from one and the same child / subject, educated in the family of authors.