 Poincaré’s controversial view was that one could never know, or better, than none was simply "true". Human beings, through evolution and through our experience as infants, pick the Euclidean group and so we say that space is Euclidean. Our bodies are quite rigid, our motions are rigid motions, and this is decisive. Another species, drawing on different experiences, could pick the non-Euclidean group and so say that space was non-Euclidean. If we met such a species, there would be no experiment that would decide the issue.