Incrementalism is a model of the policy process advanced by Charles Lindblom, who views rational decision making as impossible for most issues due to a combination of disagreement over objectives and an inadequate knowledge base. Policies are made instead through a pluralistic process of partisan mutual adjustment in which a multiplicity of participants focus on proposals differing only incrementally from the status quo. Significant policy change occurs, if at all, through a gradual accumulation of small changes, a process Lindblom calls seriality. While Lindblom sees nonincremental policy departures as extremely rare, subsequent research suggests that major policy departures may occur in response to crises or mass public arousal, through the development of a rationalizing breakthrough after many years of experience with policy implementation, or through a process of punctuated equilibrium. While many scholars and policymakers have argued that nonincremental alternatives may at times be superior to incremental ones, implementing nonincremental policy departures poses special problems and often gives way to incrementalism in the administrative process as public attention and support for strong action wane. Nonincremental policy departures are more likely to be both enduring and effective where long experience with an issue leads to consensus on values and an adequate knowledge base, giving rise to a rationalizing breakthrough. Properly understood, incrementalism is a form of what Sowell termed systemic rationality. The policy process would work more efficiently if all participants recognized the superiority of systemic rationality over what Sowell calls articulated rationality, just as Lindblom does in arguing the superiority of incrementalism over the synoptic ideal. For all its problems, our current system of polarized parties fails to eliminate the need for incrementalism. To the contrary, conditional party government makes possible a new form of partisan incrementalism that offers some advantages over traditional incrementalism.