>No, a "subsidy" is not the same as a purchase.

Did I a say "subsidy" was the same as a purchase? Not sure what you're getting at.

>Purchasing something at whatever the current market price is is just a purchase.

Um. It's a purchase. It can also be a subsidy and generally is when the government does it. If the government purchases a bunch of oranges to give away (or throw in the gutter) it is subsidizing the orange market. Are you not familiar with how government subsidies work in general?

>Fixing prices at lower than the current market price, and making up the difference in various hidden ways, which is what the government does with fossil fuels, is a subsidy.

There are lots of ways to subsidize things. Almost everything (or maybe absolutely everything) the government does creates a subsidy of some kind.

>No, it's an enormous investment in transportation infrastructure for the benefit of everyone.

It's not for the benefit of everyone though. Car-centric life obviously is not very healthy, so it's not healthy for the general public to subsidize this. More importantly, it creates dangerous externalities for people that walk, bike, etc.

It heavily subsidizes unsustainable suburban modes of living, etc. Can you imagine the shitfit people in Kentucky would have if they had to fund their own roads?

>Which benefits all transportation technologies.

Wat? How does building a 20 lane highway in Houston benefit bikers? It doesn't. It actively harms them.

How does building a road to Dingleberry Alabama benefit people that ride the subway in DC (or want to ride a subway in Alabama)? It doesn't.

>Unless you think that hybrid or electric or fuel cell or solar powered vehicles are somehow unable to use the same roads?

Again, this is taking kind of an autistic view. In theory, yes my fart-powered car can use the roads. In practice, since 99% of cars are powered by carbon, we know that a road subsidy benefits carbon users 99% of the time.

>Which is a non-answer unless you know, with sufficient confidence based on scientific knowledge (not somebody's beliefs or speculations or hypotheses), the amount of the externality and who can address it at the lowest cost.

Huh? Why would we need to know this? If my neighbor is pumping carbon dioxide into my living room, I don't need to do any calculus or science to know that (a) he's wrong and (b) he needs to stop. That is a problem that markets can't solve.

Why would we need to know the person that can do it at the lowest cost? The person doing the bad behavior should bear the cost regardless of who the lowest cost avoider is.

>Which nobody knows for the case of CO2 emissions.

We know a lot about the costs of C02 emissions. It's ridiculous to say we need to have perfect solutions before we can push back on our current failed "solution".

>First, government solutions are violent: the government can dictate what everybody does only because it can back up what it says with violence if necessary.

Absolutely. That's a huge role of the government. If some asshole is pumping carbon dioxide into my living room, the government needs to correct his behavior. If a strongly worded letter doesn't do it, violent action must (ethically) be taken to correct the situation.

>Second, you ignore the obvious third alternative: give people a better option in the market.

I'm not sure why you think I ignored this. I have literally written books on market solutions. But they can't solve everything.

>If the government did not subsidize fossil fuels, gasoline would be more expensive and more people would be buying cars that used less, or no, gasoline.

But you would still have too many people buying. You need to read up on externalities.

>No need to use force on anyone.

Yes need to use force. This is econ 101. When you have an activity that forces negative externalities onto third parties without compensation, you get
sub-optimal levels of that activity. When you don't bear the full cost for polluting the air I breath (this is very well documented stuff here) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3155438/, then you'll tend to create sub-optimal levels of pollution that wouldn't exist if you had to bear those costs.

>And if there were more entrepreneurs figuring out how to build cars that used less, or no, gasoline, they would get cheaper.

This helps but doesn't fix the problem.

>That is true even for the SUVs that you apparently abhor: a hybrid SUV can easily get double the gas mileage of a conventional one. But with gas as cheap as it is now due to government subsidies, the added cost of the hybrid simply doesn't pay for itself over the life of the vehicle.

Even without government subsidies, gas is extremely cheap.

>What I have said is that dictating a public policy to everyone requires a well-supported scientific rationale, or at least a much higher standard for one than has been used.

This is the part you still aren't addressing: We are already dictating a public policy to everyone without any scientific support whatsoever.

>Then we simply disagree. You think this claim has a well-supported scientific rationale. I don't. I think it's a combination of ideological beliefs, speculations, and hypotheses, with no predictive track record to back it up. So I don't think dictating public policy on this basis is justified. If you want to base your own choices on it, go ahead.

You're misunderstanding. You are saying that the public policy you like (lets keep it simple and say "Ford Excursions") doesn't need any scientific backing whatsoever. But the public policy I like (lets say "bikes") somehow requires a "well-supported scientific rational". You need to explain this difference. Under your system, our current policies are also not justifiable (nor are the policies you are advocating for).

>You're misstating the alternatives. The alternatives for public policy are not "keep burning carbon at current rates" vs. "burn less carbon". The alternatives for public policy are "allow people to make their own decisions about burning carbon" vs. "dictate everyone's carbon burning activities by force".

You are ignoring externalities. This line of thinking is fine for activities that don't harm others. It doesn't work if there are externalities. Unless you think I should be able to forcibly go stop my neighbor from polluting, you still haven't solved the problem.

>The former does not need a well-supported scientific rationale. The latter does.

You can't just say this without justification. Or you can, and I can too:

The former needs a well-supported scientific rationale. The latter does not.

How about that?