This paper specifies competences and skills of methodologically rational decision making and their impact on security of organisations. The study indicates some reasons for developing the competencies and skills in education, professional development and taking them into account in the recruitment. It is the practical aim of this paper. Its scientific aim is to formulate and to partly justify general hypotheses concerning the impact of methodologically rational and irrational attitudes of members of organisations on their security. We apply the method of ideal types of Max Weber and phenomenological analyses, which concern intentionality of methodologically rational and irrational mental attitudes.