Someone in mono_poly wrote about the idea that polyamory is a mechanism for a person's partner to get those needs met which that person cannot directly meet himself.
This is one of the most enduring ideas about polyamory I have ever encountered.
In my experience, it is also one of the furthest from the truth.
You see this idea expressed by both polyamorous and monogamous people. The monogamous person looks at his polyamorous partner sand says "Why am I not enough?" The polyamorous person looks at his polyamorous partner and says "Ah, polyamory lets you have the things I can't give you." Implicit in the foundation of both statements is the idea that a person is polyamorous because of the qualities of his partner.
I believe this is utter bunk.
I am not polyamorous because of the qualities, deficiencies, or shortcomings of my partners. I am not polyamorous because my wife is "not enough," and I am not polyamorous because I have a list of needs and I get those needs met from different people. My polyamory is not a consequence of the people around me at all. It would not matter who I was involved with; it would not make any difference if I were to find a partner who could meet 100% of my needs 100% of the time...I would still be polyamorous. Polyamory, for me, is a consequence of who I am, not a consequence of who my partners are, or how successful my partners are at meeting my needs.
The idea that polyamory is a way of getting one's needs met from multiple sources also contains a deeper, more subtle flaw: It assumes that relationship needs are transitive. They are not.
I do not have a list of needs, and then seek partners who meet those needs until I have met all the needs on that list. The needs of a relationship are not attached to a person; they are atttached both to people and to relationships themselves.
In many ways, a relationship between two people can be thought of as an entity unto itself. A relationship has its own needs, and in some ways has its own agenda as well. It's been my experience that relationships are most successful when the people involved pay attention to their needs, the needs of their partner, and the needs of the relationship.
When you look at relationships this way, it quickly becomes obvious that the rules of relationships do not follow the rules of mathematics. If I need A, B, C, D, and E from my romantic relationships, it does not necessarily follow that if I get A, B, and D from Suzie, and C, E, and F from Betty, I will be fine.
In reality, what is more likely to happen is that when I become involved with Suzie and Betty, I find that I need A, B, C, E, and F from Suzie, and I need B, C, D, and F from Betty. Getting F from Suzie does not mean I no longer need F from Betty--and in fact if I need F from Betty and can't have it, my relationship with Betty may suffer as a result.
Romantic needs are not transitive; people are not interchangeable. If I am getting something from one partner, that does not mean my need for that thing is now discharged and I do not need it from another partner. Romantic relationships simply don't work that way.
Bottom line: Polyamory is not about external factors; a person is not polyamorous because his partner is insufficient or because he needs things his partner can't provide. A person is polyamorous because of internal factors, which cut right to the heart of the way that person thinks about relationships, and the blueprint of that person's heart. Perhaps the polyamorous person is poly because the drive within him to seek out love and intimacy does not switch off when he has found a pertner; perhaps the polyamorous person is poly because of the way he thinks about family. Hell, perhaps the polyamorous person is poly because some subtle quirk of genetics or some environmental happenstance, or both, have conspired in such a way as to make his brain work differently than other people's.
But it's not about having more needs, or getting all your needs met, or about some inadequacy in his partners.
And that's a feature, not a bug.