Other forms: epistemologically
An epistemological argument is a philosophical discussion about the nature of knowledge and how you know what you know.
The Greek word for "knowledge" is episteme, and epistemology is the branch of philosophy that considers how you know things — how, for instance, your senses determine what you can know about the world around you. It is an epistemological view that where truth and belief intersect, one finds knowledge. Now that's deep.