# Re: 3vl 2vl and NULL

Date: Tue, 06 Dec 2005 00:05:23 +0100

Message-ID: <6jh9p11f2sl6nkalet5q4bihv2uctb1gq1_at_4ax.com>

On 4 Dec 2005 16:36:54 -0800, JOG wrote:

*>
**>Roy Hann wrote:
*

>[snip]

*>> If you have a Boolean variable then you know that its missing value must be
**>> drawn from only the Boolean domain. The appropriate way to think of the
**>> missing information is therefore not as an empty set, but as something that
**>> is simultaneously all possible values from the Boolean domain. The Boolean
**>> variable thus might be T, F, or T/F (where T/F is a kind of superposition of
**>> all permissible Boolean values).
**>[/snip]
**>
**>I wonder if you are heading for a more probabilistic approach here? I'd
**>contest that something can simultaneously possess all possible boolean
**>values, but it can certainly have an equal probability of being one of
**>those values (Schroedinger's boolean?). That would allow a
**>probabilistic truth table:
**>
**>T & T = 100% T
**>T & F = 100% F
**>F & F = 100% F
**>T & U = 75%T 25% F
**>F & U = 25%T 75% F
**>U & U = 50%T 50% F
**>
**>I suggest this only out of curiosity (to my mind a missing field means
**>no matching proposition full stop, but lets leave all that m'larkey to
**>the other thread).
*

Hi JOG,

I'm sorry, but the probabilistic truth table makes no sense at all.

Let's start with this:

Okay. You don't know my age. You do know that 5 > 4. Now consider the proposition

(5 > 4) & (Hugo OLDER THAN 40)

With your probabilistic truth table, this whole expression has a 75% chance to be true - so there's abviously a 75% chance that I'm older than 40. Based on what? And how would my chance to be over 40 change if I use this expresion:

(5 > 4) & (6 < 7) & (2 = 2) & (3 != 5) & (Hugo OLDER THAN 40)

But it gets worse. Let's move to

And consider

(5 = 4) & (Hugo OLDER THAN 40)

According to the probabilistic truth table, there's a 25% chance that this expression is true. Well, I can tell you - if I ever reach the age where 5 suddenly becomes equal to 4, I'll seak suicide.

Best, Hugo

-- (Remove _NO_ and _SPAM_ to get my e-mail address)Received on Tue Dec 06 2005 - 00:05:23 CET