Our next task is to study certain fundamentals in regard to the different ways in which levity and gravity are found to be intertwined in combustible substances, manifesting through the difference of their relation to the process of combustion - that is, the process by which levity is restored to its original condition. It is the aim of the present chapter to show that by doing justice to the imponderable aspect of combustion, the way is opened to a view of the 'elements', as scientific chemistry understands them, which will be in line with our dynamic conception of matter.