I join the crowds who say "What kind of fool question is this?" and "Monogamy is not Santa Claus". Does monogamy care whether I believe in it? Would monogamy exist if I didn't believe in it?
But the intent of the question!
I believe that it is possible, in general, for some human beings to behave monogamously. I believe that some human beings are wired to pair-bond monogamously. I know that I am one of the humans that requires an intense pair-bond in order to behave monogamously, and that forcing me to behave monogamously in the absence of that pair-bond is a recipe for disaster.
I also know that it is unlikely for me to achieve a mutual pair-bond like that at this time. So monogamy can go suck it.