The language faculty is internal to, and shared by, each of us (members of the human spices). Discovery of its properties necessarily involves discovery of universal aspects of the language faculty, i.e., aspects of the initial state of the language faculty (borrowing Chomsky's exposition). If we try to discover aspects of the initial state of the language faculty by the most widely accepted method in a natural science (the hypothetico-deductive method -- dubbed by Feynman (in Lecture 7 of his 1964 Messenger Lectures at Cornell University) as the "Guess-Computer-Compare" method), our predictions must be based on hypotheses about universal aspects of the language faculty and they must be as definite as possible. We must also articulate exactly how such hypotheses, combined with other hypotheses, give rise to definite predictions and how such predictions can be tested experimentally. This then means the need to articulate various aspects of prediction-deduction, experimental design, interpretation of experimental results, among other issues.

One of the basic issues has to do with what we should consider as evidence for or against our hypotheses in language faculty science. I state in the draft of Chapter 1 of Language Faculty Science: "There are no restrictions, determined prior to our empirical investigation, as to what can be regarded as evidence for or against our hypotheses about any subject matter. This applies to the study of the language faculty. But, no matter what kind of evidence we might consider, it should be revealing about the subject matter―in our case about universal properties of the language faculty. Since the language faculty is, by hypothesis, what underlies our ability to relate linguistic sounds and meaning, it seems reasonable to consider the informant judgment on the relation between linguistic sounds and meaning as something that we can use to test the validity of our hypotheses about the properties of the language faculty. We leave open, of course, the possibility that other types of evidence may serve the same purpose and provide converging evidence for our hypotheses."

This leads to the position stated in [44337] "Anaphora, inside or outside the language faculty," under [44324] "Some Chomsky videos":

Being an internalist, I ultimately do not believe anything unless I can test it in my own Lab (i.e., against my own judgments) and unless I see the proposed hypotheses in fact deduce definite and testable predictions that get supported experimentally (i.e., in a single-researcher-informant experiment with myself being the sole informant).

An empirical generalization, claimed, adopted, or predicted, in a given work, about any language must be stated at least in part in terms of a hypothesis about universal properties of the language faculty in such a way that, combined with other hypotheses, it gives rise to a definite and testable prediction. If I fail to see that, I do not know how to evaluate it, as a language faculty scientist.

In language faculty science as an exact science, it is not good enough to state empirical generalizations in "theoretical (and presumably, universal)" terms. Empirical generalizations and predictions must be stated crucially on the basis of a hypothesis about universal properties of the language faculty (combined with other hypotheses). Furthermore, not only is it necessary to clearly state how exactly the predictions are deduced from hypotheses and can be tested experimentally, it is also of utmost importance to try to put forth hypotheses in such a way that it would be as easy as possible for others to show them to be invalid. That is a key feature of testability-seeking research, if we take the methodological naturalist approach seriously, and hence adopt the hypothetico-deductive method (i.e., the Guess-Compute-Compare method).

One might find it difficult to imagine how one can pursue what is suggested above in research that deals with the language faculty. (That seems understandable in light of how research has been done in the past and how students are trained in the field that deals with language and the language faculty.) My forthcoming book Language Faculty Science addresses how we can do that.