1. Do Mormons believe in polygamy?

Depends on what you mean.

We don’t teach it or practice it on a day-to-day basis, but polygamy permeates our history and it’s still hugely present in the temple and our scriptures. So we “believe” in it but we don’t “believe” in it, if you get what I mean.

2. What do you think about polygamy?

As a religious principle, I don’t believe in it and won’t practice it. I think it was a big, messy experiment started by Joseph Smith and I’m glad it’s gone. I don’t know what I would have done in Joseph Smith’s day. I have a lot of sympathy for Sarah Pratt. I think it should be excised from our current practice, and that a man should not be able to be sealed to more than one woman. Now, if people want to practice polygamy outside of the Church, I don’t control that but I agree with Jonathan Sacks’ comment:

"And the most obvious expression of power among alpha males whether human or primate, is to dominate access to fertile women and thus maximise the handing on of your genes to the next generation. Hence polygamy, which exists in 95 per cent of mammal species and 75 per cent of cultures known to anthropology. Polygamy is the ultimate expression of inequality because it means that many males never get the chance to have a wife and child. And sexual envy has been, throughout history, among animals as well as humans, a prime driver of violence."

Cosmologically, things are a little more tricky. I believe in the sealing power, I believe in the temple, but I also believe that our actual knowledge about human relationships in the afterlife is slim-to-none. I have a supreme testimony in the goodness of God and the knowledge that our Heavenly Parents want us to be happy. That’s about as far as it goes.

...

5. Why did we have polygamy?

I don’t know. I believe that Joseph Smith was sincere in his religious experience. I don’t think polygamy was instituted to satisfy his lusts. I also think JSJ had a grand vision of a great family in the eternities that we have largely adapted and abandoned since his death, in part because we no longer practice the laws of adoption. The arguments about needing to protect widows are hooey. We need to find ways to preserve that cosmic vision of each of us inseparably connected, without the proprietary nature and utter exclusion that comes with polygamy as practiced here below.