The one or one of many?

I'm going to get philosophical on you today, so put on your thinking caps.

I've often wondered if there really is only one person for each of us, or if there are several people with whom we are capable of falling in love and living happy, content lives.

Let's look at "the one" theory first. Certainly, this is the most romantic of the theories. There are 6.6 billion people in the world (and counting), so if you're lucky enough find that one person who's right for you, that's really something special. One the other hand, that also means you only have a minuscule chance of finding your soul mate. "The one" theory maintains that another person is your other half, and without that person, you are not complete. This theory is perpetuated in Hollywood with quotes, like the one from Jerry Maguire: "You complete me." Classic.

Now onto what I'll call "the one of many" theory. This theory states that there is not just one person in this big, big world for you, no; there are actually several people who you can love and cherish and lead a great life with. It's definitely the most reasonable, the idea that you can be compatible with many people. But it also can be mind boggling. How could your life change if you chose one lover over another potential lover? This theory is more commonly found in real life, as widows and widowers find they are able to find love again after the death of a spouse.

The practical side of me wants to stick up for "the one of many theory." But my romantic side wants to believe I've found "the one."

What do you think? Is there such thing as "the one?" If so, how do you know you've found it?