Week 6, Day 5
Wrote pseudocode/documentation for deterministic and probabilistic counterfactual implementations.
Did some more research into the "find closest world" mechanism, and found this very useful paper from Pearl, 1994. It explains the drawbacks of this approach as follows:
"To account for such uncertainties, (Lewis 1976) has generalized the notion of “closest world” using the device of “imaging”; namely, the closest worlds are assigned probability scores, and these scores are combined to compute the probability of the consequent. The drawback of the “closest world” approach is that it leaves the precise specification of the closeness measure almost unconstrained. More specifically, it does not tell us how to encode distances in a way that would (1) conform to our perception of causal influences and (2) lend itself to economical machine representation."
As such, it appears as though Pearl's definitions of deterministic and probabilistic counterfactuals are more modern approaches to Lewis' imaging technique. I'll have to look further into Lewis' literature to understand how the closest worlds are assigned probability scores.