For any (alleged) generalization that we might have seen, heard, or might want to "use" or think of, I suggest that we check and see how the predicted schematic asymmetry is deduced by what (universal and language-particular) hypotheses, how the prediction can be tested, and whether we obtain a confirmed predicted schematic asymmetry in accordance with the prediction, in line with the methodological proposal summarized under Methodology [42404].

If we fail to obtain a confirmed predicted schematic asymmetry, that means something must be wrong, and the continuing use of such an alleged generalization is likely to result in more confusion (if one is interested in language faculty science as an exact science) than anything, although it may contribute to the creation and expansion of "a swamp over which the paralyzing vapours of the publication explosion hold an eternal sway" as Popper 1974: 977 puts it. For the methodological issue behind this, please see the thread under Methodology [29073].

Popper, K. 1974. "Replies to My Critics," in Paul Authur Schilpp ed., Volume 2 of The Philosophy of Karl Popper, The Open Court Publishing, La Salle, Illinois, pp. 961-1197.

An important omission here is that confirmed schematic asymmetries, even when they are not deduced from (universal and language-particular) hypotheses, can still be considered as a candidate for a "fact" in language faculty science. If an alleged generalization fails to constitute a confirmed schematic asymmetries -- whether or not it is predicted -- it does not qualify even as a candidate for a "fact" in language faculty science, for the reasons stated in the postings under Methodology [42404].