Thread by @EpiEllie

Interested in thinking more deeply about what a “cause” is? Causation: A Very Short Introduction from @ranilillanjum and @SDMumford is a great starting point.

Thread recap starting now👇🏽#twittereview #epibookclub #causation #causalinference #epimethodsclub

Chapter 1 sets up the problem: causation is hard to define, both in general & for specific events. It’s more than just temporal ordering, but is it a separate thing?

An ex., a town gets sick after flood of rats. Did the rats cause sickness? Maybe it was actually a sick visitor.

Chapter 2 introduces us to Hume’s theories of causation.

1st, regularity: sometimes things are *regularly* followed by other things.

Is this causation? If so, how regular is regular enough? How many times do we have to observe steam after heating water to say it’s causal?

Another take, constant conjunction: for heating water to *cause* steam, then heating and steam need to constantly seem conjoined — one event following the other.

But, this definition can’t rule out ‘accidental’ correlation.

Chapter 3 adds 2 more criteria: temporal priority and contiguity. That is, causes should precede effects; and cause & effect should be spatially adjacent.

Temporal priority is nice because it creates the asymmetry that causation seems to exhibit: causation has a direction.

But, if the cause must happen first and the cause & effect must coincide in space, how does causation “transfer” to the effect?

Maybe spatial adjacency also requires temporal adjacency — that is, maybe cause and effect have to occur at the *same* moment in time for causation?

Chapter 4 adds Hume’s final component of causation: necessity. This is a clear flaw — causes don’t always “work” in real life, but that doesn’t make them less causal.

We can have competing or interfering causes, or a cause made up of complex parts that can fail.

#causalpies

Chapter 5 is all about counterfactual dependencies—if causes are things that make a difference, how do we think about what ‘make a difference’ means?

An interesting note: sometimes what will happen is fixed by definition. This is a counterfactual dependence but *not* a cause!

A nice quote👇🏽that I think is probably very relevant to the #welldefined vs just do(it) approach to #causalinference in #epi vs #compsci today.

Another interesting part of chapter 5 is the discussion of what *exactly* are counterfactuals? Are they imaginary? Do they really exist in some other, parallel, universe? Are events causally related because of counterfactual dependence? Or vice versa?

An illustrated glossary of terms:
(1) overdetermination: watering the plant isn’t required for growth because it also rained, so no counterfactual determination.

(2) sine qua non: Big Bang is strictly required for eating pizza for lunch but is not what we would consider a cause.

Chapter 6 is about physicalism—can we think of causation as a physical process like transfer of energy?

If we do, then we can finally explain ‘accidental’ conjunction (in this👇🏽example, the explanation is confounding)

Energy transference also gives us directionality which is an important competent of causation.

But! Sometimes the direction of energy transfer is not the direction we think of for causation...

Chapter 7 is about pluralism — maybe there isn’t just one definition of causation for all cases. Maybe causation is a family of things ...

Aristotle believed this. He had 4 types of causation depending on the level at which you wanted to understand an effect.

But, accidental correlations also have ‘family resemblance’ to causation... so pluralism doesn’t help us rule them out.

Maybe the reason we can’t explain causation is that it is a foundational concept — a most basic thing that can’t be broken into smaller parts. This is the topic of Chapter 8: primitivism.

Chapter 8 also interrogates the idea that we can’t sense or experience causation directly, we can only see relationships or conjunctions.

For example, we don’t see causation when a diver jumps off a springboard, we only see that the board bends.

Previous chapters looked at causation from the outside, but people are causal agents: we can decide to do things and make them happen.

As causal agents, maybe we *can* directly sense at least some causation. For ex, when we lift something heavy we sense & respond to weight.

The final philosophical approach is Chapter 9 — dispositionalism. Maybe causation isn’t a *thing*, it’s a *potential* for something.

A glass that is fragile has the potential to break, but doesn’t just smash spontaneously. Maybe causation works the same way.

Problem: where does the ‘causal’ disposition live? In the effect? in the cause? What about in nothingness—sometimes a lack of things is a cause of harm...

The book wraps up with a (very) brief discussion of the history of causal inference, touching on Pearson, Fisher, and @yudapearl’s causal diagrams, and ending (spoiler alert?) with Hills’s causal viewpoints which my #epi readers will know all too well.

So, what is a cause? My takehome from this book is that even after more than 2000 years, philosophers don’t really know.

Even though most humans feel like they know what causation is and can recognize it when they see it, it’s not at all easy to put into words.

So where does that leave us?

Perhaps our best option is to become doctors of causation: look for characteristic signs & symptoms, & try to rule out alternate explanations.

Which is exactly what we do in #epi!
So we may not be real doctors, but maybe we’re #causaldoctors😄