How could our culture in less than 50 years move to affirm Gay Marriage? Epistemology

We might wonder how our American culture in the space of only 50 years could go from a small minority affirming gay marriage to a majority. What underlies such a rapid change is the epistemological changes which have taken place during the last 50 years. We don't answer questions like, "how do I know what I know" and "how do I know what is true" as our parents and grandparents did. Three means of confronting the post-modern thinking of our culture are discussed.