Mathematics and logic are subjects of a special kind, which stems from their formal character. Basically, mathematics and logic are often viewed as empty formal manipulation of symbols. However, this opinion hides the constructive character of the topics. The constructive steps in mathematical and logical reasoning bring new information into the reasoning process which allows us to see mathematical and logical reasoning as dialog. Connecting this dialogic character to Platonic approach we can understand the dialog as foundation of education of mathematics. The approach of the paper is basically philosophical. However, we connect philosophical discussion to present-day pedagogical discussion in which dialog is taken seriously. We will show that there are interesting interconnection between (formal) mathematical reasoning and proper dialog.