Trying to find an answer to the question when we can
say that we have knowledge I found an article by Baron Reed titled
“Fallibilism” (Philosophy Compass 7/9
(2012): 585–596). In a section of this article Reed discusses the Lottery
Paradox and its relevance for knowledge as justified true belief. The paradox
has been described first by Henry E. Kyburg, Jr, in 1961. I must say that, like
the Gettier cases debate, I didn’t follow the discussion that developed since
then, so maybe my arguments against it are not new (but I didn’t get the
impression when I read Reeds article), but it is interesting to treat the
paradox here because of its significance for our concept of knowledge.
I start with Reed’s description of the Lottery Paradox
(id, pp. 588-589):
“[The lottery paradox] depends on the following two
principles:
1. If it is highly probable that p, then it is rational to believe that p.
2. If it is rational to believe that p and it is rational to believe that q, then it is rational to believe that p & q.”
These two principles are quite plausible, so Reed, and
if the “two propositions are each rational to believe, then surely it is
rational to believe their conjunction. … Nevertheless, the two principles
together yield a counterintuitive result. Suppose there is a fair lottery in
which 1000 tickets are sold and in which only one ticket will win. For each
ticket, there is thus a .999 probability that it will lose. Principle (1) tells
us that it is rational to believe of each ticket that it will lose. So, where
proposition pi is the
proposition that ticket ti
will lose, it is rational to believe that p1,
that p2, …, that p1000. Principle (2) tells us
that it is rational to believe the conjunction of all these propositions: that p1 & p2 & … & p1000.
But, because we know it is a fair lottery, it is also rational for us to
believe that some one of the tickets will win – i.e., it is rational for us to
believe that either not-p1,
or not-p2, …, or not-p1000. We know (and
rationally believe) that this is equivalent to the proposition that not-(p1 & p2 & … & p1000).
Using principle (2) again, it is rational to believe that p1 & p2
& … & p1000 &
not-(p1 & p2 & … & p1000). But that proposition,
of course, is a contradiction.”
At first glance, the Lottery Paradox may seem
plausible, indeed, but at second glance? Premise (1) says that it is rational
to believe that p if p is highly probable. But why should it?
For example, I work as a security officer on an airport where I check the
passengers at the gate. It is highly probable that the next passenger is a decent
person and not a terrorist. Nevertheless, for me it is rational to believe that
he might be an exception. The only thing that is rational to believe is that p is highly probable and not that it certainly
will happen, as premisse (1) seems to state. Otherwise we add information
without any argument.
Take now premise (2). What Reed doesn’t make clear is
what “&” means. Say I throw the dice. Then there is a probability of .83
that 1-5 will come up. If I throw several times, that doesn’t change for each independent (separate) throw. If we interpret
the & for separate throws, the probability for each throw remains .83. However, now we interpret & in the way
that the first throw p is 1, 2, 3, 4,
or 5 and the next throw q is and
the next throw r is etc.. Then after
four throws the probability is 0.83x0.83x0.83x0.83=0.48 that this will happen, which
is already less than a half! In other words, if p, q etc. are dependent on each other in some way and they
have probabilities of less than 1 it is not rational to believe that p & q & etc. (i.e. in my example that each time 1-5 will come up).
This brings me to another flaw in the lottery
paradox. Even if the premises are true, the world is wider and it contains also
other knowledge, for instance what statisticians say about probabilities. Our
rational believe is not based on single isolated facts but it is interwoven
with other knowledge, like statistical knowledge. And statisticians can tell us
that it is simply not true that we have to analyse the probabilities of the
1000 tickets in the lottery as independent
from each other: If we know that one
lottery ticket will not win, then the probabilities that the other tickets will
win increase. Knowing the probabilities of the separate lottery tickets as such tells us nothing about the
probabilities when we put some (or all) tickets together, unless we do the relevant statistical computations. I think that more
can be said against the Lottery Paradox, but it is clear that neither premise (1)
nor premise (2) is correct. The upshot is that there is no Lottery Paradox.