This thesis explores ideas about the limits, prerequisites, and objectives of investigating nature, primarily but not exclusively through astronomy, at work in the writings of Islamic scholars including Ibn al-Haytham, al-Ghazālī, and several astronomers of the Marāgha tradition. The latter tradition of modified Ptolemaic astronomy answered both Ibn al-Haytham's call for conceptual and predictive consistency and al-Ghazālī's for metaphysical hesitancy appropriate to human reason's limitations. Virtuosity and rhetoric, spirituality and one-upmanship, and perhaps even artistry evident in the Marāgha astronomers' proliferation of ingenious models highlight an elective quality that bridges the 'motivation gap' between their ongoing model-making and the lack of more tangible motivations, revealing the humanity behind their enterprise. Al-Ghazālī, once thought a destroyer of Islamic science and philosophy, truly helped give shape to a distinct and distinctive style of astronomy as an exploration of God, the heavens, and the bounds of human knowledge.