Scientific evidence is indeed vital to public policy. The pandemic has made this undeniable, if it was not already obvious enough. But science does not offer a repository of neutral evidence that arrives, ready-made, onto the political scene. On the contrary, scientific knowledge is an achievement, the result of a complex process in which the judgment of scientific experts — call it expert judgment — plays a decisive role. Utilizing such knowledge to make policy decisions is even more complex, requiring not only expert judgment but also the judgment of those non-experts — call it non-expert judgment — whose experience, knowledge, or know-how is also needed to deliberate well about the best course of action. It follows that judgment and deliberation are not secondary, lesser processes, that we must rely on when integrating scientific evidence into the policymaking process. Rather, judgment and deliberation are essential to this process, in part because they are essential to science itself. Failure to appreciate this fact risks engendering unrealistic expectations about what scientific knowledge can accomplish in practical decision-making, thus inviting not only disappointment, distrust, and skepticism, but also bad policy.
In what follows, I will make a case for this alternative account of scientific knowledge by examining the role that expert judgment plays in scientific reasoning. I will then consider what implications this account has for how we understand practical decision-making informed by scientific knowledge. I conclude by suggesting that integrating scientific evidence into public policy is by nature deliberative, a reciprocal process in which both expert and non-expert judgments must play roles, and which requires that both experts and non-experts act with prudence.