How Realistic Is It?

For all my school life (which is coming close to an end btw) I have always been against learning by heart. I always believe that if you get the idea behind it, you can come to the same conclusion yourself, if you had learned by heart. I try to follow this philosophy whenever I can.

Beginning with the time I started learning about openings in chess, I tried to follow the same philosophy. I thought that as long as I don't make stupid mistakes (there are lots of them as you will probably know) you could come out of the opening just fine. By all means, learning about these mistakes and not repeating them is much easier and more logical than learning these openings by heart.

However, when I read posts here, or check similar websites, people are crazy about lots of kinds of openings. They know a lot of openings by name and even by variation. I don't. I only know a few, and just the first 2 or 3 moves. Rest of the game I try to come up with my idea of openings in chess.

What do you guys have to say about this? Is it realistic trying to be successful in chess without memorizing openings?

i would say you can get to about 2000 level whitout knowing alot about openings.

Most chess players obsess way too much over openings. I agree that you can get to 2000, or at least 1800 (OTB, which is around 2000+ here online) without knowing much about them. It's a decent idea to learn the basic traps for any opening you play, so you can avoid them, but don't waste time memorizing long variations.

Understanding the reasonings behind the move-orders is much more important than memorizing them. If you learn this way you will benefit at far above the 2000 level as well.

and how to you learn the reasoning behind them?

You can't be successful in chess without opening knowledge. You maybe can get a 2000 rating, but at this level you should have your repertoire worked out.

I think your approach is OK, but you might want to pick a few openings to specialize in, as different openings have different tricks and traps for you to know and to avoid.  Trying to learn about mistakes for all the openings takes a long time and might not be as helpful in the long run, especially if you seldom play some of the openings.

By analyzing games played by grandmasters and coming up with your own opinions?

^ I highly recommend Capablanca: move by move.