I like to occasionally peruse Henry's wonderful list of principles that make aikido work. Lately I've been working my way through this list, blogging about my thoughts on each one, and I've worked my way up to #3
Nothing Ever Works
Also occasionally stated as, "I wouldn't bet my life on THAT!"
All martial arts have assumptions and presuppositions. Axioms that they use as starting points. One of our most foundational assumptions in aikido is that it is near-useless to rely on strength and speed to get things done because (again, we assume) the bad guy is always bigger, tougher, stronger, faster, and more clued-in to the circumstances of the attack. This assumption makes sense because weaker, slower, smaller folks don't usually try to victimize more powerful people. So, it's not too bad a starting point to assume that you're always going to be the underdog.
Being the underdog means that Nothing Ever Works. Any time you try strength, he's stronger. Any time you try speed, he's faster. Any time you use your skills, he's more skilled.
This means that you have to build your martial art based on strategies that do not require abnormal amounts of strength, speed, or skill to work. Your techniques have to be robust and fail-soft, and everything has to have a back-up plan. If you have the co-ordination and athletic skill that it takes to stand up and balance and walk around at a fast walking pace, then you have enough athleticism to make aikido work. If you are strong enough to push or pull a heavy door open, then you have enough strength. And by the time you get to about green belt (around 60 mat hours) you have just about all the knowledge and skill that you need to make aikido work pretty good.
It's a crazy sort of near-paradox.
Aikido works because we start out with the assumption that nothing we do will ever work.
It's crazy, but it works.