What makes a burden on religious exercise “substantial”? This question stands at the center of recent religious liberty debates. Pursuant to the Religious Freedom Restoration Act (RFRA), government cannot "substantially burden" religious exercise—unless doing so is the least restrictive means to achieve a compelling government interest. But defining what qualifies as a substantial burden has proven quite slippery. To determine whether a law’s impact on religious exercise is theologically substantial would seem to draw courts into a constitutionally impermissible assessment of religious doctrine. Yet to avoid a substantiality inquiry altogether would ignore a core feature of RFRA’s text. To navigate this dilemma, this chapter proposes that courts examine not the religious substantiality of the burden. Instead, courts should assess the substantiality of civil penalties triggered by religious exercise. Doing so ensures that courts can apply RFRA’s statutory standard without running afoul of Establishment Clause concerns. In turn, courts can adequately apply RFRA, providing a workable method for distinguishing between those claims deserving of RFRA’s protections and those that are not.