disinterest

She eyed him over her martini with cool disinterest.

He maintained a posture of scrupulous disinterest in Balkan affairs […]

Now the progress of Knowledg being stopt by extreme Confidence on the one hand, and Diffidence on the other; I think that both are necessary, though perhaps one is more seasonable: For to believe that every thing is certain, is as great a disinterest to Science, as to conceive that nothing is so: