In Metaphysical Foundations of Natural Science (1786), Kant attempts both to specify in principle what "proper" science needs to be, and then concretely to establish, as far as possible, that an a priori, mathematical physics could be reconstructed that would entail the Newtonian laws of mechanics and of gravitation. In specifying so rigorously what "proper" science requires, Kant consigns a great deal of empirical natural-scientific inquiry to a lesser status. This was particularly problematic for the emergent fields of chemistry, geology, and biology. Furthermore, even with the arguments of the third Critique it is not clear that Kant secured the validity or "propriety" of empirical laws or of their integration into an "order of nature."