By constraint on the light of the inner senses, knowledge of the subtle, concealed and distant.
‘As within, so without’, ‘As above, so below’ and ‘what’s here, is elsewhere’ are dictums that perfectly illustrate extrasensory perceptions and their functions. Just as there are physiological instruments called the eyes that perceive external objects through sight, likewise there are parallel instruments internally that perceive subtle, concealed and distant or remote phenomena and objects. This applies to all of our senses with the pivotal agent being the mind that is either focused externally and hence limited by space and time or internally constrained breaking the bounds of what is commonly known and understood as space and time.
What the mind can perceive, it can conceive and develop understanding of.