I am in the process of reading Causality, the seminal book by Judea Pearl, from cover to cover. I have been previously exposed to the potential outcomes framework – the graphless approach, so to say, which is widespread in econometrics and statistics, and this is my first serious attempt at understanding the directed acyclic graph (DAG) framework, besides listening to the absolutely awesome lectures by Brady Neal while driving.
I find the clarity of the graphical approach mind blowing. It is definitely the way to go if you plan to actually get anything done. Yet there is something fishy at the philosophical level in assuming the possibility of atomic interventions –say acting on obesity without changing either the diet, the exercise regimen or any other biochemical or metabolic quantity, to take an example from Pearl’s article.
I find it obvious that there must be fundamental physical limits to the atomicity of interventions, or to interventions altogether –we are always part of the system we act on, in a way. It seems that one should formalise this by merging the theory of dynamical systems and that of causal inference/discovery.
What causes what? Credits to u/Cppnv
I see a parallel with the Newton/Leibniz debate on relationism: getting calculations done in coordinates is so much easier than working with ratios between pairwise separations of particles that one is ready to throw out all his philosophical qualms for the sake of, you know, actually being able do to any mechanics at all. Doing the right thing –philosophically speaking- sometimes requires so much effort as to be impractical.
If, back then, we could accept absolute space and time –alongside with the relevant theological implications[1]- to be able to work out the trajectory of cannon balls and rockets, should we also be ready to accept thinking the do-operator without any guarantee that it can actually be implemented by some Hamiltonian?
To be entirely frank, I am very wary of the concept of causality altogether. Ultimately, it’s metaphysics: structure we wish to impose on the data from the outside[2]. The graphless camp complaint that immutable characteristics should not be regarded as causes –being un-manipulable- should apply to everything. Counterfactuals just are not, and one should not be allowed to think them; and in fact it’s surprising that the big question mark on counterfactuals raised by quantum theory seems yet absent from this debate.
[1] I can’t help thinking that calling the Prime Mover a ‘universal confound’ sounds extremely poetic
[2] Apologies to any philosopher reading this.
This: https://ui.adsabs.harvard.edu/abs/2008JSMTE..04..001A/abstract