Even physically indivisible atoms would still be aggregates of distinct parts, and an invincible attachment of parts does not overcome the diversity of those parts.

According to Leibniz, bodies (qua material) are aggregates, and an aggregate, of course, is not a substance on account of its lack of unity. The claim in the above passage is that whatever being or reality an aggregate has derives from the being and reality of its constituents. Thus, Leibniz thinks that if a body is to have any reality at all, if it is to be more than a mere “phenomenon, lacking all reality as would a coherent dream,” then it must ultimately be composed of things which are real