We examine how and why missions emerge during social venture organizing processes. Through a real time longitudinal grounded theory study of seven nascent ventures, we discovered that prosocial motivations take distinctly different forms and that differences between how empathetic versus sympathetic founders conceive of those needing help drives differences in processes leading to mission emergence. We discover and theorize forms of passion that expand prior conceptualizations of entrepreneurial passion. Our findings provide a theoretical footing for research on the creation of social ventures while our model ties the creation of such ventures to mainstream approaches in entrepreneurship and organization theory.