Either (i) they try to domesticate the object of puzzlement by providing a reductive or explanatory theory of it; or (ii) they declare it irreducible and hence not open to any levelling account; or (iii) they succumb to a magical story or image of what seems so puzzling; or (iv) they simply eliminate the source of trouble for fear of ontological embarrassment...
The topics on which it imprints itself, and which I have discussed in some diagnostic detail in the aforementioned book, include: consciousness and the mind-body problem, the nature and identity of the self, the foundations of meaning, the possibility of free will, the availability of a priori and empirical knowledge... Basically what we find, quite generally, is the threat of magic or elimination in the face of the theoretical obduracy of the phenomenon that invites philosophical attention.
The distinction between science and philosophy is, on this view, at root a reflection of the cognitive powers we happen to possess or lack, and is therefore creature-relative: it does not correspond to any interesting real division within objective reality...
It is not beyond the bounds of possibility that our brains would have to be made of something other than neurons in order for us to have the kinds of cognitive powers needed to solve the problems philosophy poses; at any rate, this is the sort of diagnosis [transcendental naturalism] offers for our philosophical retardation...
The hardness of philosophy is thus an upshot of the particular way that natural selection has built our thinking organ, not an objective trait of the subject-matter of philosophical questions.
[8]As argued in Kant's Critique of Pure Reason, human thinking is unavoidably structured by categories of the understanding: Quantity – Unity, Plurality, Totality.
Thomas Nagel mentions the possibility of cognitive closure to the subjective character of experience and the (deep) implications that it has for materialist reductionist science.