A comparison with traders:
A trader doesn't have this paradox. A trader claims to forecast prices, therefore he can say that as long as the odds favour the price rising (or, to be more accurate - as long as the odds favour positive trade expectation), it is rational to stay long.
In the scenario with stock X where it falls $80 to $40 and then back to $80, a trader can rationally buy at $40 if the odds favour a price rise, then hold all the way up to $80 (and even higher) so long as the odds keep favouring further price rises more than declines. At each tick higher, so long as the odds favour price rises, it's rational for a trader to hold on.
Obviously this requires him to know the odds with some degree of confidence. But at least he has a rationale for holding. The value investor has no such rationale, unless he starts claiming to be able to predict prices too - yet most value investors say they are making NO prediction of prices.
A trader doesn't have this paradox. A trader claims to forecast prices, therefore he can say that as long as the odds favour the price rising (or, to be more accurate - as long as the odds favour positive trade expectation), it is rational to stay long.
In the scenario with stock X where it falls $80 to $40 and then back to $80, a trader can rationally buy at $40 if the odds favour a price rise, then hold all the way up to $80 (and even higher) so long as the odds keep favouring further price rises more than declines. At each tick higher, so long as the odds favour price rises, it's rational for a trader to hold on.
Obviously this requires him to know the odds with some degree of confidence. But at least he has a rationale for holding. The value investor has no such rationale, unless he starts claiming to be able to predict prices too - yet most value investors say they are making NO prediction of prices.