It's turtles all the way down. The deeper you dig, the more turtles you'll find. At the surface there are cute little turtles, turtles you can touch and see and even speak to. If you listen close enough you might hear what they have to say in return. We call these Level 1 turtles. Level 1 turtles are the facade turtles, the interactable turtles, the surface level turtles, if you will.
One day you find your first shovel. Maybe it is a common garden trowel. Maybe it is a Fendt backhoe or a flat-head spade or your bare fingernails. Whatever your shovel is you start digging, and you discover Level 2 turtles. These turtles are superficially understandable to you when you find them. You could have gone your whole life without knowing about these larger, crusty turtles. Once you break into the Level 2 turtles, your sense of reality is altered a bit. Not significantly, your taste in bagels doesn't change overnight. The strength of your sense of smell doesn't switch with your sense of sight, à la being able to smell how uncomfortable your neighbor is with their unexpected dinner guest's topic of conversation but can only see in black-and-white for 20 feet. None-the-less there is a distinct reality shift.
Once knowledge, achieved through digging, on Level 2 turtles is found; the realization hits. "How many Levels are there, really?", you ask yourself late at night. "How can I return, back to when I was happy existing on the Level 1 turtle plane, not even aware that there was more to life than what I now refer to as 'Level 1' turtles?", you ask. During the day on long walks you find your thoughts stray to things like "Well, how many Levels are there actually?" and "Do I need a bigger, shinier shovel or can I just work harder with this Better Value brand plastic garden trowel?"
And then the fear sets in. That lingering thought pierces your mind. "It is turtles all the way down, isn't it?"
Sadly, the inverse isn't true. It isn't turtles all the way up. Well, thankfully, I guess for some of us. Knowing that there is just pure fresh air above is admittedly comforting. No grimey Level 2 turtles. But now, after returning to the surface for the first time, consuming sustenance and interaction, you look at those Level 1 turtles in a different light. I mean, it isn't like how you look at your neighbor differently after you learn they give out goddamn juice boxes to children on Halloween. It is more similar to...appreciation. Level 1 turtles are well built. They're strong, cute, robust. But most importantly they hide everything about the Level 2 and beyond turtles. You now appreciate the fact that some person(s) had spent so much time and effort polishing their shells, etc. etc.
After that first ascent to the surface, you have a realization. You understand too much and too little. You must return under the topsoil with your excavation implement. You might seek wisdom, knowledge, or just a pure sense of curiosity. Regardless, you return and start delving. Deeper. Darker. We'll say you reach the Sub-Level 2 turtles. These turtles are still well within the realm of Level 2 turtles, but these are the cusp of Level 3 turtles. This is where you realize that the level of turtle abstraction is worrying.
Welcome, you've transitioned from whimsey to worry. From wishful to weary. You realize, "Hang on, everything is built on these base layers? These layers that are 'solved problems', and those who are in the pre-Level 1 realization phase (aka those who still view turtles as turtles and not an allegory for something specific to themselves) rely on this foundation dearly and don't even realize it? These graham-cracker-cheesecake-crust Layers have existed for how long, how many people have touched them, and how unfinished are these Levels really?" Then you realize, "Hey now, underneath this crumbly buttery 'cookie' (are graham crackers considered cookies?) crust is...what? A layer of grease, followed by the glass pie dish, a thin air gap, then the kitchen counter?"
This is what is called pre-enlightenment. Where there is fear there is a lack of understanding. Only when that fear is replaced by terror, by unimaginable fright, by mental anguish you wished you had as a teenager, by true emotional discomfort we come to post-pre-enlightenment. Still not quite enlightenment, but we're getting there. Slowly but surely.
Regardless, finding the Level 3 turtles requires a level of specialization. It requires time and energy. You must 'pay your dues' however 'dues' are not some social construct they're seconds and minutes and hours and days and weeks and years and decades and...well not centuries really the human life span is limited but you know, time. To breach Level 2 you must forego breaching Level 1 in some other area. It is a sweat realization that some other turtles will not even have the realization that they are Level 1 turtles, they'll always be turtles to you.
I like to think of this as a time bank. Your time bank has debits and credits. 'Level breaching' is good old fashioned double-entry book-keeping. To be truly effective, you must manage your time in a GAAP like fashioned. Your fastidiousness in where your debit your seconds and credit your hours must give Luca Pacioli a raging erection. To be good at something you must be bad at others. This is fine, the natural course of the world. Ben Carson might have been a great brain surgeon but not a good historian.
It is hard to say if there are really levels beyond Level 3. The turtle Leveling system varies for some species of turtles. A true gift is seeing where these turtles cross over in the Level 1 and Level 2 and Level 3 striations. Ascending from your little turtle-dom is worth more than it's weight in turtle-gold.
As you already know, it's turtles all the way down.