I think we have to distinguish between different kinds of love here, a la Doctor Helen Fisher. There’s lust, romance and attachment. Opening up your relationship for the purpose of lust with a 3rd party is significantly different than doing so for the purposes of attachment. Additionally, there’s unilateral and bilateral polyamory. The former doesn’t include the involvement of your partner. When I think about polyamory, I’m not necessarily thinking about ménage à trois.