Your ideals in life conflict, and you aren't both able to assert your own at the same time that your lover is asserting theirs. Your lover is naturally much more accepting of ideas that involve speculation and intuition than you are, and they have a hard time representing them to you, as you insist on proper proof. When they can't give it -- after all, who can prove the intangible, like love or hope or faith?
-- they may start doubting themselves and their beliefs. On the other end of that dynamic is you, thinking you have a very good reason for challenging your partner's ideals; in your mind, their ideas are baseless. They seem to you as if they have no foundation in anything that can be properly trusted, much less understood, and that to you translates as worthlessness. Your ideals have been developed through careful weighing of the alternatives and consideration of all angles, so you tend to distrust anything that involves 'gut reactions' or anything else that's hard to put your finger on. But your perspective denies an entire facet of human experience. You two have a hard time communicating the importance of your own point of view, because you aren't able to respect each other's.