I have the impression that sincerity, earnestness and straightforward conviction used to be more popular flavors of attitude and have been replaced (at least in the public sphere) by more self-conscious, ironic, critical, half-hearted, cool type attitudes. I went hiking with a friend today, and he mentioned the same impression (though I may have got mine from him), and we speculated about the reasons.

Does everyone share this impression? Over what time-scales? Do we have good explanations?