According to Wikipedia,
<<Research can be defined as the search for knowledge. Three types of researches are mentioned:
(1) Scientific research
(2) Research in the humanities
(3) Artistic research
Artistic research has been defined by the University of Dance and Circus (Dans och Cirkushögskolan, DOCH), Stockholm in the following manner - "Artistic research is to investigate and test with the purpose of gaining knowledge within and for our artistic disciplines. It is based on artistic practices, methods and criticality. Through presented documentation, the insights gained shall be placed in a context." Artistic research aims to enhance knowledge and understanding with presentation of the arts.>>
If we replace the word “artistic” by “metaphysical”, the definition will read:
"Metaphysical research is to investigate and test with the purpose of gaining knowledge within and for our metaphysical disciplines. It is based on metaphysical practices, methods and criticality. Through presented documentation, the insights gained shall be placed in a context."
The last sentence in the quoted paragraph will read:
“Metaphysical research aims to enhance knowledge and understanding with presentation of the various fields of metaphysics.”
Therefore, please do not demand that metaphysical theories to go through the steps of validation by independent scientific tests.
Well then, how do we know that the theories are true? Through research we can enhance our knowledge and understanding. We can scrutinize documentation by our predecessors. We can practice to see whether we achieve a result and document our findings. Since the knowledge of metaphysics is not a collection of some rigid rules, it can be enhanced to perpetually improving without the goal of perfection because perfection in metaphysics does not exist.
The word Science comes from Latin scientia, meaning "knowledge". The science as defined today is only one kind of knowledge that can satisfy certain definitive rules. If someone demands all other kinds of knowledge to go through the same rules, then a religion called “Science” is established. Do you want to be the founding infallible Pope of this religion?