How do you know he's The One?

A few years ago I traveled to Australia on my own (don't get me started on how depressing it is that I have to now say 'a few years ago' when referring to my trip). I had just graduated college and had no idea what I was going to do next. So instead I took off to a foreign country in hopes of avoiding having to make a decision. I pretty much wandered around the country for a little over a month. Truthfully I probably would have stayed there if I hadn't just bought a condo. For those of you who know me know that I am not the most out going person; mind you, I have my moments but I dance of the verge of shyness most of the time. When I was traveling around Australia I was this person, this person who was free to let the wind blow her wherever it wanted. I slept in different towns, I tried different foods, I met different people. The best part about the people I met was that I knew I would probably never talk to any of them again. The freedom you feel knowing you will never see someone again is amazing. This goes for both men and women; the conversations were fun and free, deep and profound at the same time. There were a few guys that are worth mentioning... There was the Canadian drinker, he was older but sexy and he bought me drinks. He probably only bought me drinks because I was the only one who would stay up drinking and laughing with him until 4 am but either way, he bought the drinks and we had great conversations. I met the Danish student. For as much as we talked, I really don't remember a single thing about him. I met the funky guy American guy from Southern Cali who was wondering around the world until he found the place he wanted to live. I also met the Canadian engineer. He was 28, he was a scruffy handsome ourdoorsy type and he was the kind of guy who turned down the offer from him company to pay for his vacation in a 4 star hotel to stay in hostels because he knew he would rather be surrounded by people his own age than with stuffy 45 year old guys. He was funny, he was smart and he secretly loved Prince (as do I). He love to dance, he was a good dresser and loved to travel. What else could you ask for? I sat there thinking to myself, I wonder if I should go talk to the guy at the bar? I was completely, utterly disinterested in this guy. On paper, I would have been head over heels in love with this scruffy Canadian engineer. But I could have cared less about him. What is that special little thing that makes you cross the line between thinking 'he's a nice guy' and thinking 'he's a NICE guy'? What makes the difference to your heart when you are presented with 2 guys that look the same on paper? What is it that makes him The One?