We can surmise certain things. Verification is not always possible nor necessary. If we see a plane flying...we can surmise that it has been created by Intelligent intervention. It is obvious. Similarly, we can also surmise that life has been created by intelligent intervention. Religions attempted to explain this through mythology.
The problem arose when cosmology, theory of evolution etc. contradicted religious beliefs. It was thereafter assumed that if the universe functions through natural laws and if human life has evolved through millions of years....then there cannot be any intelligent intervention.
This assumption is clearly wrong as I have argued in another thread. Evolution or the existence of natural laws do not automatically rule out intelligent intervention.
We can indeed suggest intelligent intervention has created the plane flying, but in the broader sense, we cannot assume so at all, as it is evolution that has created brains which can design aeroplanes, just as it is evolution that created the brains to create spiders' webs. The origin of that evolution is the creation of life and so far we have no complete and satisfactory answer as to how life began. What we can say, however, is that there is no evidence whatever to support the idea that life was created by intelligent intervention. Indeed, even if one 'surmised' that life was created by intelligent intervention, one would also have to surmise that the origin of this intervention had a particularly imperfect intelligence, and the whole idea would quickly become impossibly complicated.
Yes, problems arose when scientific understanding contradicted some religious beliefs, but that was mainly a problem for those holding such contradictory beliefs. There is no assumption that there cannot be any intelligent intervention, only that there is no evidence whatever for such intelligent intervention and therefore science has no obligation to pursue this line of thought unless or until evidence is forthcoming. Furthermore, evolution doesn't need the input of any intelligent designer as an explanation at all. It works perfectly well without one(or more than one).
This, of course, is a long way from saying 'there cannot be any intelligent intervention' as you quite rightly say, although I would have thought that this is purely conjectural and belongs in the realms of religious and spiritual thought, rather than science, for the reasons given above.
