The Summary of Physics Restored

58Experience teaches us that all compound bodies are resolved by analysis into dry and moist, and that all animal excretions end in those same distinctions. From this it is clearly evident that compound bodies are made from only two sensible elements, corresponding to earth and water, though the others are present in them in power and potentiality. Air, or the element of the lower heaven, escapes the senses because in relation to us it belongs in a certain way to the order of spiritual things. Nature's fire too, being a formal principle, cannot be detected and separated by any analytic destruction or ingenuity of art. For the nature of forms is not subject to the judgement of the senses, because it is spiritual.