 We come across a different kind of hypothesis and fully perceive its productivity. Undoubtedly, the theories seem at first sight fragile and the history of science shows us how fleeting they are. However, they do not entirely die out and something remains of each of them. It is this something that we must try to sort out, for there and only there is true reality (Poincaré 1902: 26; 2017: 3–30).