The linguistic analysis of the pericope John 9,1-41 is carried out. First the problem of blindness in the Bible is shortly presented. Then the seven parts of the pericope are analysed from the point of view of the vocabulary, the syntax and the semantics. Then it is pointed out how each part shows us the role and the meaning of testimony as a way which may lead both the person giving it and those listening to it closer to the full knowledge of the Lord.