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A hypothetical and theoretical acknowledgement that there might be things we don't know about is par for the course. Attempting to reflect that in either language or actions is less than helpful.
I take you to mean effectively that the hilited part "goes without saying", that it is the correct scientific stance: we are always open to new data overturning our models, as long as the data is sound. [sarcasm](For Navigator's benefit, here I am using "sound" in the British vernacular sense of "logically consistent, or based on solid foundations")[/sarcasm]
The correct formulation of that in either language or actions would be to assume that the models we have are sound and complete, until such time as new data demonstrates an inadequacy in the model.
This assumption of completeness is based on the twin facts that there is no data that we currently have that is not adequately accounted for in the current model, and there is no prediction of the model that can not in principle be observed to actually occur. (Here we have to allow "observe" to include the effects of the entity in question, as with subatomic particles we observe their effects through the bubble chamber tracks which are not the particles themselves, but the effects they have on the liquid in the bubble chamber under the influence of the magnetic fields within the chamber, etc… or indeed, the effects of the force of gravity, even though we cannot observe a gravitational field directly: we have seen no gravitons, and indeed gravity is a conventional word for the effects of the curvature of space-time in Relativity, for instance).
This is why I say it is futile to speculate that there could be an as yet undiscovered "force" which could shoehorn a ghost experience into the physics model we have. There is no undiscovered force required to explain any of the observations we have made.
I've just made this up, and although I've studied physics and maths with the Open University, I have not studied the philosophy of science, so I may have formulated this all with a naive expression. I'm not 100% sure I've got the second of my "twin facts" correctly expressed in the third paragraph here.
I'm just trying to express my understanding of "possible" in the context of what I understand as science.
I'm open to adjustment, if anyone here has more than sophistry to offer in commentary on my statements.