Sustainable development might have several constituents, among which the different aspects of public participation have a paramount relevance. If one examines the given topic – sustainable development and its constituents – there are always some vital new elements worth talking about, among which public participation is at the core. A vital fresh and illuminating element in the field of environmental sustainability is the Encyclical Letter of Pope Francis of May 2015, which discusses sustainable development and environmental issues in detail. A kind of motto for the whole Encyclical is provided in point 13: “The urgent challenge to protect our common home includes a concern to bring the whole human family together to seek a sustainable and integral development, for we know that things can change.” It is not our task to introduce this remarkable document in detail, but we must point to the special role of public participation in the whole enigma.