Metaphysical notions are often met with criticism. The same goes for those who engage in the practice of metaphysics. Such criticisms can be addressed or challenged. It is arguable that metaphysics is the foundation for everything and is, thus, the most important subject in any attempt we might make to improve our knowledge of the universe. I will sometimes argue for this point in articles on this blog, but the basic principle is that whatever we can claim to know about anything at all has to be put into some framework or viewed within some context. The framework functions as a backdrop theory for whatever it is that we are claiming or investigating. The denial of such a theory denotes a hard form of skepticism wherein no knowledge of anything is possible apart from the direct
experience of the senses and the tautologies of mathematics.
But even the most die-hard philosophical skeptic is forced to relax his positions when faced with carrying out his everyday activities. Whether he likes it or not, the extreme epistemological skeptic has to have a basic framework of beliefs — if not to do philosophy, then to live.
Some also argue that because metaphysics is neither falsifiable nor verifiable, then any claims made by metaphysics are meaningless. Furthermore, the same arguers will likely tell you that any attempt at describing the whole of reality can be expressed in terms of the concepts used to describe each and every part of reality and would, thus, be insufficient on its own. Nonetheless, we find a range of concepts and principles employed in the physical sciences that are, in fact, metaphysical notions. Energy and gravity are but two of them.