Many of the ideas used by the investment community are adopted from the horse track and casino betting communities. Much of the failure that has dogged the investment community is due to rocket scientist PhDs misunderstanding the successful models of plebeian punters. The use of betting as an example is not an endorsement, just history.
To understand how the securities markets work you have to look no further than the horse bookies. Bookies take the bets from the bettors. This is the first point that the public begins to misunderstand how betting, and therefore investing, works.
There are two potential misunderstandings: The first misunderstanding is assuming that each horse has a uniform probability of winning, i.e. they are all just as likely to win. The second misunderstanding is assuming that the bookie offers one to one payout odds, i.e. pays $1 for each $1 that is bet. Grasping the significance of these statements is the key to successful investing.
The bookie, equivalent to the investment bank or broker, will always make money. Always. They do this because they do not set payout odds depending on which horse they think will win, they set payout odds based on how people bet.