A great householder named Shaunaka once came to Angiras and reverently asked:
"What is that by knowing which all is known?"

He replied: "The illuminated sages say knowledge is twofold, higher and lower.
The study of the Vedas, linguistics, rituals, astronomy, and all the arts can be called lower knowledge.
The higher is that which leads to Self-realization."

    Lower knowledge is mental knowledge, brain knowledge.  It comes from reading books and from studying the material world.  Science, math, economics, etc. is lower knowledge.  There is nothing wrong with such knowledge.  On the contrary, we need it to survive in a material world.
    Higher knowledge is spiritual knowledge.  It comes to us from the Logos.  Gnostics and mystics call it Gnosis.  We receive it in visions, dreams and symbols.  It is a language the soul understands but not the brain.  Gaining this knowledge in full is called self-realization, Christ consciousness, Enlightenment, etc.  While some limited amount of this knowledge may come to us spontaneously, we usually have to seek it out to get it.