This chapter argues for both a broad similarity and a crucial distinction between the ways in which Lucretius (De rerum natura) and Seneca (Naturales quaestiones) employ the category of the sublime in their natural scientific (including cosmological) writings. Both authors, as previous scholars such as Gian Biago Conte and Gareth Williams have observed, use the sublime as part and parcel of their didactic and consolatory projects. Moreover, in both authors the sublime first causes the pupil-reader to "take fright" in the face of nature and then builds him up to conquer nature with his own knowledge. Yet in Lucretius and Seneca the knowledge that allows such conquest is quite distinct: for the Epicurean, scientific knowledge is limited, while for the Stoic, it approaches omniscience.