Or as it's caricatured by a self-help motto you've probably seen: if you think you can, or if you think you can't, you're right.
- Markets are composed of many people with different expectations - does it matter that the price level reflects a weighted average of a range, instead of a single opinion held by the whole market?
- Do expectations and prices really move instantly, or do illiquidity, imperfect information and bounded rationality mean that they take some time to change? If so, what if expectations change again before the price catches up? Will the arbitrage opportunity implied by the rational expectations ideal ever really exist?