3 ms·
Follow-up: I think I found some relatively unambiguous claims in the paper to help get a handle on the logic. After "Theorem 2", there's a "Proof" with multip
by _Nat_ 4y ago
Follow-up: I think I found some relatively unambiguous claims in the paper to help get a handle on the logic.
After "Theorem 2", there's a "Proof" with multiple lines directly equated. Among those lines were
> = 1 - p(h,eb) - p(e,b) + p(he,b)
> = p(h←e,b) - p(h,eb)
, which can be equated to and reduced to find
1 = p(h←e,b) + p(e,b) - p(he,b)
, and then if we take the condition of "b" as assumed for brevity,
1 = p(h←e) + p(e) - p(he)
, then it appears that the conditions of "h←e" and "e" cover all possibilities, plus an excess overlap of "he".
So, "h←e" refers to NOT(e) plus AND(h,e).
So, "h←e" equals OR(NOT(e), AND(h,e)).
So, the evidence "e" implies the hypothesis "h" when both are true, plus also when evidence "e" is false.
---
So, "Theorem 1" claims
p(h←e, e) < p(h←e)
, which we can now parse given the above to
OR(NOT(e), AND(h,e)) when e < OR(NOT(e), AND(h,e))
, and we can reduce the left-hand side to find
h when e < OR(NOT(e), AND(h,e))
h when e < NOT(e) + AND(h,e)
h when e < NOT(e) + (h when e) * e
0 < NOT(e) + (h when e) * e - (h when e)
0 < NOT(e) + (h when e) * (e - 1)
0 < (1 - e) + (h when e) * (e - 1)
e - 1 < (h when e) * (e - 1)
1 - e > (h when e) * (1 - e)
1 > h when e
, or to write that last line out,
p(h | e) < 1
, which matches out with the condition that they attached to "Theorem 1", which requires that p(h|e)!=1.
But to work that out with the sides keeping their values,
h when e < NOT(e) + (h when e) * e
h when e < NOT(e) + (h when e) * (1-NOT(e))
h when e < (h when e) + NOT(e) - (h when e) * NOT(e)
h when e < (h when e) + NOT(e) * (1- (h when e))
h when e < (h when e) + NOT(e) * (NOT(h) when e)
, which appears to be the last line of their "Theorem 2".
So.. I guess that explains the definitions that they were using.
---
Anyway, what seems odd to me about that is that "Theorem 1" seems like it's meant to be surprising -- like it's meant to show that finding evidence reduces the meaningfulness of the evidence itself, or something?
However, some things seem off. For example, the expression of "h←e" seems weird to me; it'd seem more sensible for it to be like this:
OR(AND(NOT(e), NOT(h)), AND(h,e)) when e < OR(AND(NOT(e), NOT(h)), AND(h,e))
h when e < OR(AND(NOT(e), NOT(h)), AND(h,e))
h when e < (!h when !e) * !e + (h when e) * e
0 < (!h when !e) * !e + (h when e) * (e - 1)
0 < (!h when !e) * (1 - e) - (h when e) * (1 - e)
0 < (!h when !e) - (h when e)
(h when e) < (!h when !e)
, where the inequity isn't obviously of particular interest.
Because the second thing that seems off is the notion that this matters -- that the evidence, "e", should be a concern for not just figuring out the probabilities in the model, but also retro-actively adjusting the meta-model, or something?
In short, after tracing their math and such, it's unclear what point they might be trying to make, as this doesn't seem surprising or unexpected.