As the Covid-19 shutdown enters its second month, policy makers and commentators have emphasized that we’re not yet out of the woods. Deaths and hospitalizations are continuing to rise, albeit more slowly than before. The flattening curves have encouraged some people to talk about reopening the economy, and others to rise in protest against ongoing restrictions, but most Americans remain cautious. We’ve been willing to endure the staggering economic damage because we’re convinced that it’s necessary for public health—and that the lockdowns won’t last too long.

Indeed, a kind of conventional wisdom has emerged among public health officials and policy experts. We’re told that life will go back to normal just as soon as we’ve reached a series of public health milestones: near-universal testing, the development of effective treatments, the emergence of herd immunity and, ultimately, approval of a vaccine.

But this conventional wisdom has a critical flaw. We’ve taken for granted that our ingenuity can solve almost any problem. But what if, in this case, it can’t? What if we can’t scale up coronavirus testing as quickly as we need to? What if it takes us six or 12 months, instead of three, to identify an effective treatment for Covid-19? What if those who recover from the disease fail to gain immunity and are therefore susceptible to getting reinfected? And what if it takes us years to develop a vaccine?

Once we start asking these questions, a terrible truth becomes clear: The scenario in which we meet all the public health milestones, and then return to our regularly scheduled economic programming, is highly optimistic. A more realistic scenario is that we will fail to reach one or more of the milestones. If that happens, do we prolong the economic shutdown for six months or longer? Do we impose a series of on-and-off stay-at-home orders that could go on for years?

The damage from a prolonged economic shutdown is difficult to contemplate. Tens of millions of Americans have already lost their jobs. Countless small businesses have closed—many for good. Two months ago, 20% unemployment seemed unthinkable. Two months from now, 20% unemployment might seem like the good old days.