The article discusses the benefits and losses of the European Union's enlargement in 2004 using a philosophical and synergistic approach. The authors analyze the impact of the enlargement on three levels of knowledge: philosophical, geopolitical, and political/economic/social. They suggest that the experience of Central and Eastern European countries can be helpful for new applicant countries. The changes at the political, economic, and social levels are most noticeable, shaping the overall image of the event.