The connection between epistemology and metaphysics is that epistemology justifies what otherwise would be "improvable" knowledge, moving concepts into reality. Without epistemology, nothing in metaphysical study would have any sort of authority or weight. This is critical because metaphysical beliefs or concepts cannot depend on traditional scientific methods to be proven true.
To understand the connection between epistemology and metaphysics, an individual must grasp what each subject is. Metaphysics is the study of all things not in the physical realm — physical studies are handled through true sciences. It is a philosophy that investigates why things exist. It uses concepts to explain the realities people experience.
Epistemology and metaphysics are similar in that both are branches of philosophy, but as a field, epistemology concentrates on knowledge, looking at what makes knowledge true or justified. Put another way, epistemology seeks to answer how a person can prove that what he believes, identifying the elements that make information part of a reality set. It also focuses on the characteristics, sources and limitations of knowledge people have.
A person cannot use traditional scientific methods to prove metaphysical beliefs. In fact, metaphysical concepts sometimes directly conflict with science. For example, an individual cannot conduct a test to see whether a god exists or whether the creative process is happening. Thus, metaphysicists must provide other evidence that what they experience is reality. They must use epistemology to explain why their concepts can be viewed as absolute, producing rationalizations for each metaphysical belief.
Understanding that metaphysicists cannot rely entirely if at all on science, epistemology is critical to the acceptance of the metaphysical. In the scientific community, the more evidence — that is, data — a person has to support a hypothesis or idea, the more people see the idea or hypothesis as justified. In the same way, when a metaphysicist produces a great deal of evidence toward his concept, the more weight the concept comes to have and the more meaningful it becomes. People come to see the metaphysical idea as highly likely to be true or as a reality and do not dismiss it as easily.
When properly connected, epistemology and metaphysics explain not only the non-scientific truths people hold, but also how those truths came into being and how they have shaped reality. They also allow individuals to place trust in things that the scientific community cannot necessarily explain. This gives an individual a broader sense of the world, how things function and what might be possible.