Obviously this history does not mean that just because a plan is divisive or unpopular, it will necessarily turn out to be a good idea. But it illustrates two instructive realities.

• The first, which is plain fact, is that big choices are rarely easy choices. Precisely because of their scale and impact, they involve tradeoffs, imperfections, pros and cons.

• The second, which is my opinion, is that big infrastructure investments are usually under-valued and over-criticized while in the planning stage. It's much easier to envision the here-and-now costs and inconveniences, and harder to imagine fully the eventual benefits. That's not true of all of them, but it's how I read the preponderance of American-history evidence from the Louisiana Purchase onward.

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With that context, let's go back to California's ambitious and thus naturally controversial plan to build a north-south high-speed rail system. In the previous installment, I gave the basic pro-HSR case.

For today, a survey of the opposition, which I will lay out as fairly as I can, saving responses for an upcoming post. Here's why I'm happy to do so:

Even the most stalwart supporter of the original Medicare plan, or today's Obamacare, had to know that there were uncertainties and drawbacks. Big decisions are more often 55-45 than 90-10. You have to weight the pros and cons, the knowns and unknowns. I think the pros still prevail in this case, but we have to look at the cons.

The main claims are:

• A high-speed rail system might be great in theory, but the realities of this plan fall far short.

• It will cost too much, take too long, use up too much land, go to the wrong places, and in the end won't be fast or convenient enough to do that much good anyway. And, from some people,

• It's an old-tech band-aid to a problem that really calls for a "disruptive"-tech fundamental solution, from self-driving cars to the Elon Musk-style hyperloop.

You can see a lot of the objections in one place in a dispatch conveniently titled "7 Ways James Fallows is Wrong About the CA Bullet Train." Also see this from RealClearPolitics on the deteriorating politics of the HSR plan within California.

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And here is a sample note from a reader in California, on the challenges the plan now faces:

I am very supportive of a high speed rail network in theory; very few people I have talked to are not. Driving between Los Angeles and San Francisco is a good 8 hours, while by plane it is a 45-minute hop, plus the two hours and massive frustrations of the airport; neither option is optimal. People already commute two hours one way between the Central Valley and the Bay Area, daily. Outside of the reflexively anti-government types who would oppose any state project, most people can see the attraction of the idea. However, the actual execution of the high-speed rail plan is what has gone and lost my support. While a high speed land connection between Los Angeles and San Francisco would certainly make money, the high initial investment is obvious. Shorter segments between San Francisco and Sacramento, Los Angeles and Las Vegas, or even Los Angeles and San Diego would make money almost immediately. However, none of those things is what they are building. Instead, they are building the line between Bakersfield and Merced, with the further extensions only in later phases at undetermined dates. The line between these two cities would be, basically, useless; to attempt a simile to another part of the country, this would be as if the Acela didn't go between DC and Boston, just between Trenton and Newark. Its actually even worse, since unlike Trenton and Newark, Bakersfield, Fresno, etc. have no public transit to speak of, and so the train would only be useful for stranding you at the train station. However, while they are still planning and seeking funding for the further portions, this is all the line will be, and knowing California, this situation will last for years (it's already taken us six to even get to this point). Building this section first, without connecting any major population center to any other, therefore seems like an investment with no hope of a return. In the meantime, the people already opposed to the system (which are particularly numerous in the Central Valley) will be joined by those opposed to government waste in general, who will point to a train that has already cost billions of dollars and still connects nowhere to nowhere, and say, "enough, pull the plug, this has been a waste of money." Once that happens, the political realist in me has to acknowledge that there is no way promises of "but if we extended it further, it would actually work" would get any traction, and the idea would be dead. As I have remarked with my friends, only half-jokingly, if they wanted to kill the idea of high speed rail in California forever, they couldn't have gone about it much better than this. To this pessimistic political outlook, I could also add the accusations of mismanagement of the funds already spent, and the compromises that are watering down the project as it moves along (portions of the line are now not even going to be high-speed), but those are already documented by actual journalists. My main feeling, though, is that if they wanted this to work, they should have gone about it any other way than what they have.

Next up: how the plan could still be sensible, in the face of critiques like this.