The post-truth society facilitates diminished scientific authority and superficial political belief. The flag of ‘science for policy' as an imaginary counterpart again falls under a mud wrestling between incumbent leaders. Going beyond conventional citizen science and public engagement, a prospective participatory approach is positive engagement in dark science. Dark science is reflective and reflexive scientific activity with a sense of anxiety, fear, sympathy or sadness against disruptive impacts as a corollary of scientific development, by reference to structural science-society issues and planetary boundaries in the Anthropocene. Flying away from human-centric interests and thoughts on the ground, it aims to understand, talk and collaborate each other with objects arousing a sense of weirdness or wonder. Positive engagement is to nudge the less-engaged to voluntarily and positively engage in science and its policy. Dark science and positive engagement is reciprocal to make sense of our life and the world to come.