To improve pupils' motivation for and attitude towards sciences as well as their inquiry skills, we introduced P4C in Flemish science classes using a design-based research paradigm. 12 to 14 year-olds participated in several P4C sessions, focusing on the nature of science and scientific concepts. Based on both qualitative and quantitative research data, landmarks on the conditions of a successful introduction of P4C in the science class were pinned. The quantitative data show an increase in pupils' abilities to cope with uncertainty. The qualitative data suggest that participants show an increase in the ability to ask creative questions and problematize scientific concepts. P4C sessions with a mix of both thinking and scientific experiments appeared most successful. We observed that the use of philosophical dialogues may positively influence the inquiry skills of pupils as long as there is a good classroom atmosphere.