#yogasutrachallenge: The qualities of nature arise in four stages: the particularized, the un-particularized, the defined, and the undefinable - Patanjali Book II Sutra 19
In this rather vague-sounding sutra Patanjali is explaining there's a lot more to the world than meets the eye, and points to the door behind which lies understanding how the ancient yogis (and even some modern-day ones) were claimed to have psychic abilities supernatural powers.
We used to think that what we could perceive was pretty much all that existed. Then we invented telescopes and microsopes and instruments for measuring sound, energy and all kinds of things and realised otherwise. The only thing even the best scientists know now is how little we have really seen of the universe across space, time and dimensions.
In line with Sankya philosophy, as Patanjali's referring to here, nature is an undefinable force or energy which evolved into the 16 tangible elements of her realm: the 5 elements (earth, air, fire and water), the 5 subtle elements (sight, sound, taste, touch, smell), the 5 organs (speech, hands, feet, anus and genitals), and the mind. What we don't perceive is what lies these tangible elements and the raw essence of nature. This is the un-particularized land which requires psychic senses to be perceived. Our intelligence (Buddhi), is like mother nature taking a "defined" form in the natural, with training, we can open our minds to some of her hidden beauty.