Conservatives have also mistaken adherence to Reagan’s principles with the repetition of his program. Reagan’s agenda in 1981 applied a conservative philosophy to the challenges of the moment. To combat Soviet adventurism he initiated a defense buildup, engaged in ideological warfare and aided proxies overseas. To control inflation, he supported a painful tightening by the Federal Reserve. To spur growth, he cut tax rates.

Circumstances have changed since 1981, in large part because of the success of Reagan’s program. In some respects conservatism has adapted to new conditions. Entitlements have become a much larger share of the federal budget, and conservatives have accordingly made controlling them a much higher priority.

But in other respects conservatism has calcified. The top tax rate is now 35 percent, not 70 percent. Yet many conservatives act as though the current tax rate is just as much an impediment to growth as the old one, and consider its further reduction just as high a priority as it was then. The inflation rate has been trending downward since 1980, but most conservatives are more convinced than ever that money is dangerously loose.

Conservatives aren’t wrong to want to ensure that incentives to work and invest are robust, or to favor a predictable, rules-based monetary policy. But these principles have to be applied to the circumstances in which we find ourselves, not the ones of 1981.