How does a child start to construct representations? How are connected drives and objects? Why does a child begin to seek objects? What happens in the primary process thinking? Ignacio Matte Blanco said that primary process thinking and secondary process thinking are operating with different logic. I would use the name Group logic to describe logic in the unconscious. Can Group Logic help us to understand those questions? Simultaneous use of two different logics discriminates human thinking from computerised thinking. Set theory is a mathematical theory. However, applying set theory to primary thinking helps us to shed some new light on phenomena like myths, dreams, transference, and metaphors. As an example of thinking with sets, we use the Oedipus myth as a story where different parents of Oedipus (Laius and Jocasta; Merope and Polybus) may represent different aspects (Sexual and Supportive) of every parental couple.