I was intrigued by this also. According to https://plato.stanford.edu/entries/pseudo-science/ https://plato.stanford.edu/entries/pseudo-science/ : > However, i

I was intrigued by this also. According to https://plato.stanford.edu/entries/pseudo-science/ https://plato.stanford.edu/entries/pseudo-science/ : > However, in what seems to be his last statement of his position, Popper declared that falsifiability is a both necessary and a sufficient criterion. “A sentence (or a theory) is empirical-scientific if and only if it is falsifiable.” Furthermore, he emphasized that the falsifiability referred to here “only has to do with the logical structure of sentences and classes of sentences” (Popper [1989] 1994, 82). The reference given is: “Falsifizierbarkeit, zwei Bedeutungen von”, pp. 82–86 in Helmut Seiffert and Gerard Radnitzky, Handlexikon zur Wissenschaftstheorie, 2nd edition München:Ehrenwirth GmbH Verlag.