The dissertation examines Epicurus’ critique of science, particularly the recurring evaluation in the Letter to Pythocles that certain opinions, causal explanations, or entire sciences (e.g., astronomy) are described as “empty” (κενός, μάταιος). In contrast, Epicurus presents firm conviction (πίστις βέβαιος) as the outcome (φυσιολόγημα) of natural-philosophical investigation, which aims to provide explanations “in accordance with the phenomena” (συμφώνως τοῖς φαινομένοις). The study is guided by three methodological perspectives: philological, focusing on close textual analysis; systematic, clarifying the notion of conformity between explanations and phenomena; and history-of-philosophy, situating Epicurus’ critique in the broader context of ancient astronomy and philosophical thought. The analysis draws on astronomical texts (e.g., Hipparchus’ commentary on Eudoxus and Aratus’ Phenomena, Geminus’ Introduction to the Phenomena) and classical philosophical sources (notably the Phaedo, where the term συμφωνεῖν occurs in descriptions of the hypothetical method). “Emptiness” is treated as a key Epicurean concept, denoting flawed scientific methodology, for example when extraneous assumptions (mythological, mathematical, or otherwise) are integrated without methodological justification or ethical necessity. This concept differs from Aristotelian evaluation criteria such as truth/falsehood, accuracy/inaccuracy, or clarity/obscurity. The dissertation further examines Epicurus’ polemical stance toward contemporary astronomical practice and the emerging Platonic-Aristotelian astral theology, providing a systematic evaluation that goes beyond viewing his philosophy solely in ethical terms.