I think there's been a mischaracterization of ONEitis. While I do understand the protector/provider dynamic and I fully agree with it in the context of a healthy, mature, committed relationship, I think it's necessary to differentiate between a healthy relationship based on mutual respect and a lopsided ONEitis based relationship. In my estimation ONEitis is an unhealthy psychological dependency that is the direct result of the continuous socialization of the soulmate myth in popular culture. This western romanticized mythology is based on the premise that there is only ONE perfect mate for any single individual and as much as a lifetime can and should be spent in constant search of this 'soulmate.' So strong and so pervasive is this myth in our collective society that it has become akin to a religious statement and in fact has been integrated into many religious doctrines as feminization of western culture has spread.
I come to the conclusion that ONEitis is based in sociological roots, not only due to it being a statement of personal belief, but by the degree to which this ideology is disseminated and marketed in popular culture in media, music, literature, movies, etc. Dating services like eHarmony shamelessly marketeer and exploit exactly the insecurities that this dynamic engenders in people desperately searching for the ONE they were intended for. The idea that men possess a natural capacity for protection provision and monogamy has merit from both a social and bio-psychological standpoint, but I think that ONEitis is not a byproduct of it. Rather, I would set it apart from this healthy protector/provider dynamic since ONEitis essentially sabotages what our natural propensities would otherwise filter.
ONEitis is insecurity run amok while a person is single, and potentially paralyzing when coupled with the object of that ONEitis in an LTR. The same neurotic desperation that drives a person to settle for their ONE whether healthy or unhealthy is the same insecurity that paralyzes them from abandoning a damaging relationship - This is their ONE and how could they ever live without them? Or they're my ONE, but all I need is to fix myself or them to have my idealized relationship. And this idealization of a relationship is at the root of ONEitis. With such a limiting, all-or-nothing, binary approach to searching for ONE needle in the haystack over the course of a lifetime, how do we mature into a healthy understanding of what that relationship really entails? The very pollyannish idealized relationship - the "happily ever after" - that belief in a ONE promotes as an ultimate end is thwarted and contradicted by the costs of the constant pursuit of the ONE for which they'll settle for. After the better part of a lifetime invested in this ideology, how much more difficult will it be to come to the realization that the person they're with isn't their ONE? To what extents wil a person go to in order to protect a lifetime of this ego investment?
The other problem I have with the present definition of ONEITIS is that it completely ignores the Cardinal Rule of Relationships: In any relationship, whether romantic, business or familial, the person with the most power is the one who needs the other the least. At some point in a ONEitis relationship one participant will establish dominance based on the powerlessness that this ONEitis necessitates. There is no greater agency for a woman than to unquestioningly know that she is the only source of a man's need for sex and intimacy. ONEitis only cements this condition into the understanding of both parties. For a man who believes that the emotionally and psychologically damaging relationship he has ego-invested himself to believe is with the only person in his lifetime he's ever going to be compatable with, there is nothing more paralyzing. The same of course holds true for women and this is why we shake our heads when the beautiful HB 9 goes chasing back to her abusive and indifferent Jerk boyfriend, because she believes he is her ONE and the only source of security available to her.
The definition of power is not financial success, status or influence over others, but the degree to which we have control over our own lives. Subscribing to the soulmate mythology necessitates that we recognize powerlessness in this arena of our lives. Better I think it would be to foster an understanding that there is no ONE. There are some good Ones and there are some bad Ones, but there is no ONE. For far too long, women have ego-invested themselves, and now men as well, in this mythology as a means to counter what at times I'm sure seems a hopless quest of an idealized relationship. It's much easier to believe that there's someone "out there" specially made to be with you than to constatly face the fear of rejection. To those who believe this, saying that there is no ONE is like saying there is no God; it is perceived as iconoclastic and nihilistic, but it doesn't have to be. I've been married for almost 10 years now and I definitely feel protective of my wife and daughter. I wont deny that I have an impulse to be the provider and counselor of my home, but I know damn well that as much as I love my wife and we are a 'good fit' that were she to die or leave for some reason that I could find another 'good fit'. I don't have a ONEitis insecure relationship with my wife and in fact I'd say that if I were to adopt this ideology nothing would drive her respect for my down more.
In the absence of power the other person will assume the dominante role. For proven biological and psychological evidence, women want a man to be that protector you've defined here as well as the leader, the decision maker, the authority because of an overwhelming need for long term security. If a woman perceives that a man's ability to provide this security is in doubt, she will step into the vaccuum that he is unable or unwilling to assume. This is why you see the predominance of women as the 'head of household" these days; the husband can't be trusted to provide this security so she will grab the stearing wheel from him and drive the family. ONEitis is the single greatest contributor to this male sense of powerlessness. By it's very nature ONEitis is disempowering because it removes (or severely lessens) from a person control of their own lives.
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