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MICHIGAN v. EPA KAGAN, J., dissenting
considerations to go into the threshold finding than into the final rule. Simply put, calculating costs before starting to write a regulation would put the cart before the horse. III The central flaw of the majority opinion is that it ignores everything but one thing EPA did. It forgets that EPA’s “appropriate and necessary” finding was only a first step which got the rest of the regulatory process rolling. It narrows its field of vision to that finding in isolation, with barely a glance at all the ways in which EPA later took costs into account. See supra, at 10–11 (in establishing floor standards); supra, at 13–14 (in adopting compliance options); supra, at 14 (in deciding whether to regulate beyond the floor); supra, at 14–15 (in conducting a formal cost-benefit analysis as a final check). In sum, the majority disregards how consideration of costs infused the regulatory process, resulting not only in EPA’s adoption of mitigation measures, ante, at 13–14, but also in EPA’s crafting of emissions standards that succeed in producing benefits many times their price. That mistake accounts for the majority’s primary argument that the word “appropriate,” as used in §7412(n)(1)(A), demands consideration of costs. See ante, at 6–7. As I have noted, that would be true if the “appropriate and necessary” finding were the only step before imposing regulations on power plants. See supra, at 6–7. But, as should be more than clear by now, it was just the first of many: Under the Clean Air Act, a long road lay ahead in which the Agency would have more—and far better—opportunities to evaluate the costs of diverse emissions standards on power plants, just as it did on all other sources. See supra, at 4, 7, 9–15. EPA well understood that fact: “We evaluate the terms ‘appropriate’ and ‘necessary,’ ” it explained, in light of their “statutory con-
