Once we have taken the ...

Once we have taken the backward step to an abstract view of our whole system of beliefs, evidence, and justification, and seen that it works only, despite its pretensions, by taking the world largely for granted, we are not in a position to contrast all these appearances with an alternative reality. We cannot shed our ordinary responses, and if we could it would leave us with no means of conceiving a reality of any kind.
 Thomas Nagel

Quotes from the same author

It is prima facie highly implausible that life as we know it is the result of a sequence of physical accidents together with the mechanism of natural selection. We are supposed to abandon this naïve response, not in favor of a fully worked out physical/chemical explanation but in favor of an alternative that is really a schema for explanation, supported by some examples. What is lacking, to my knowledge, is a credible argument that the story has a nonnegligible probability of being true.
 Thomas Nagel
every subjective phenomenon is essentially connected with a single point of view, and it seems inevitable that an objective, physical theory will abandon that point of view.
 Thomas Nagel
A theory of motivation is defective if it renders intelligible behaviour which is not intelligible.
 Thomas Nagel
Life may be not only meaningless but absurd.
 Thomas Nagel
If sub specie aeternitatis [from eternity's point of view] there is no reason to believe that anything matters, then that does not matter either, and we can approach our absurd lives with irony instead of heroism or despair.
 Thomas Nagel