Final answer:
The assumption 'The spirit is either indivisible or imperfect' (e) is required to logically conclude the spirit is not a material body, aligning with dualism that separates physical and spiritual substances.
Step-by-step explanation:
The central assumption required to conclude that the spirit is not a material body, based on the given premises that all material bodies are divisible and imperfect and that everything divisible is imperfect, is option (e), 'The spirit is either indivisible or imperfect'. If we assume the spirit is perfect, it cannot be divisible (since divisibility implies imperfection), and therefore, it cannot be a material body. Thus, the argument concludes that the spirit is not material, asserting a form of dualism, where physical and spiritual substances are distinct and essentially different form one another.