This dissertation develops and tests a novel framework—Dynamic Epistemic Theory (DET)—to explain how individual-level epistemic needs shape political polarization. Literature on polarization largely ignores the foundational cognitive demands of modern voter. Across three empirical chapters using American National Election Studies (2000–2016), the General Social Survey (2004, 2014), and an original experiment, I examine how these epistemic needs—Need for Cognition (NFC), Need to Evaluate (NTE), and Need for Cognitive Closure (NFCC)—relate to and explain ideological entrenchment, affective polarization and party identification. Through DET, I also help unravel how epistemic demands have profound behavioral consequences such as social insulation. ANES data from 2000 – 2016 shows how NFC and NTE relates to polarization. Findings reveal that high NFC individuals are polarized over time, culminating in ideological entrenchment by 2016. NTE, meanwhile, exhibits a strong and consistent relationship with affective polarization but a counterintuitive negative relationship with party identification—supporting the claim that some individuals polarize not by identification but through rejection of the political ‘other.’ In terms of behavioral implications, such as political discussion with friends and family, findings are equally surprising. Contrary to the expectation that epistemic engagement fosters deliberation, I find that both high NFC and high NTE individuals often withdraw from political discussion, particularly in more polarized contexts. This suggests that strong epistemic motivation may discourage dialogue particularly because of lesser importance attached to their counterpart’s reasoning. The experimental chapter tests the efficacy of depolarization strategies based on civic engagement. While the main effects of interventions on polarization were negligible, significant interaction effects emerged: high NFC individuals doubled down on ideological preferences after exposure to opposing views, while high NFCC individuals, surprisingly, showed decreased affective polarization in response to cumulative depolarization treatments. These results reinforce DET’s central claim: polarization is not merely a product of information exposure but of how individuals with distinct epistemic dispositions process disagreement and uncertainty. Together, these findings offer a more cognitively grounded account of why some individuals become entrenched while others disengage. Epistemic needs, often overlooked, prove essential in understanding the nuanced ways individuals respond to political conflict and persuasion.