Quote from AyeYo:
That makes far more sense that how he stated it, but let me explain how I'm looking at it.
The market is biased long, purely from a historical perspective. Also, as stated by someone else, even if the market didn't trend up over time, the probability of it doubling is, in the real world, infinitely higher than the probability of it going to zero. So, again, the market is biased long. The probabilities are NOT normally distributed.
So what does that leave us with? That leaves us trying to toss a coin to make a red/black call on a roulette wheel that's biased towards black. It just doesn't work over time.