Use 'ken' to spotlight limits of understanding in technical or abstract discussions. Quantum mechanics is often beyond the average person's ken.
Pro Tip 2/3
Metaphorical Use
'Ken' can metaphorically suggest comprehension of complex or broad subjects. The universe's mysteries are not within our ken.
Pro Tip 3/3
Intellectual Humility
Use 'ken' to express intellectual humility about the limits of one's knowledge. Philosophy is within my ken, yet so much is still out there to understand.