[konjin]

>Physics demands that we respect electricity and don't increase the infrared opacity of the atmosphere.

Physics does no such thing. It tells us that increasing the heat retained in the atmosphere increases the planets surface temperature. It is a descriptive science. Not a prescriptive one. Wanting to have industrial civilization possible in the next century is why you don't increase the infrared opacity of the atmosphere. But that is a value judgment far outside the scope of physics, and one social sciences claim is theirs by right of ... something.

The metaphors people use to think about the natural world are terrible, or as Carl Sagan put it Demon-Haunted.

The reason why physics, and other hard sciences, are so useful and respected is that you can switch dependent and independent variables around with a lot of success.

If I have the ideal gas law:

PV = nRT

Then I can rearrange it and be fairly confident it still works.

P = nRT/V

If you are an engineer this is a godsend. You want to set a hard value for P but can only directly control V or T? Try the second equation! You have a chance at succeeding without having to spend decades building machines that blow up and kill everyone around them!

Politicians see that and are jealous. Surely if those lame eggheads can get things to work like that we can too. So the social sciences give you equations as well. After a bunch of statistics we see that:

time spent in school = a*wealth - c

We can't control wealth, but we can control how long people spend in school:

wealth = (time spend in school + c)/a

So if we force everyone to stay in school until they are 50 everyone will have 20 million dollars in their bank accounts.

And to anyone who asks how this works, politicians say: Why are you against science and hate poor people?

[tomrod]

This is why knowledge of causal inference is essential.

Causality is not established via tweaking a correlation or regression analysis, and we social scientists should know that.

[konjin]

Casual inference is the bottom most rug of what gives hard sciences its power. It is that we understand the objects we are manipulating at a much deeper level so we don't sound like idiots.

Suppose that we take:

g = ma

A perfectly valid way to find experimental values for gravity at a location. But that doesn't mean that if we push an object really hard we increase the gravity in that location, or decrease it if we pull on the object. Just because symbol manipulation gives as an answer doesn't mean that the answer makes sense, you need to keep track of all the implicit state of the universe.

[tomrod]

> so we don't sound like idiots.

I'm fine sounding like an idiot so long as my slope is increasing :)

Right, Judea Pearl covers this in [i]The Book of Why[/i].