@fresco,
In the epistemological question "How do we
know X", the ontological status of X is presumed to be agreed. For example, in the statement "how do we know the universe is expanding" the nature of "universe" as
a thing understood is not questioned. But "universe" is by no means an agreed concept as any physicist will tell you. It follows that what we
know depends on the nature of what we think "exists" ....an ontological question, but conversely the nature of that "existence" depends on our knowledge of what properties that existence implies....an epistemological question.