mjhjmtu

In the given context, I would use elusive:

To illustrate the elusive concept of anatman, the parable of
Nagasena and the King likens the mind to a chariot;

elusive

1. Tending to elude capture, perception, comprehension, or memory: "an invisible cabal of conspirators, each more elusive than the archterrorist [himself]" (David Kline).
   


2. Difficult to define or describe: "Failures are more finely etched in our minds than triumphs, and success is an elusive, if not mythic,
   goal in our demanding society" (Hugh Drummond).

American Heritage® Dictionary of the English Language

Examples of use from Google Books:

It’s a notoriously puzzling and elusive concept, usually leading to
such questions as, "If I don’t have a self, who’s reading this
sentence?"

Furthermore, this work depicts not a pastoral scene, but the fierce
struggle between man and the elusive concept of Buddha nature.

... the vast body of literature that brought the elusive concept of
shunyata (emptiness) to the forefront of Buddhist practice and belief.

The idea of Nirvana is the most important part of the Buddha's
doctrine, it is also a most elusive concept.

I found a perfect word after putting 'mysterious' into a thesaurus

Abstruse Difficult to comprehend

How about Recondite?
It's usually used in the context of something that is difficult for people without good knowledge in the subject to understand.

The image of the chariot as a "mechanism" (i.e. both the sum of its pieces and something more), suggests the word intricate:

To illustrate the intricate concept of anatman, the parable of Nagasena and the King likens the mind to a chariot; a chariot is not a pole, nor a wheel, it is the sum total of its parts.

Intricate American Heritage

adj

1. Having many complexly arranged elements; elaborate: an intricate pattern; an intricate procedure.


2. Difficult to understand, analyze, or solve for having many interconnected elements.

See also the derivation:

[Middle English, from Latin intrīcātus, past participle of intrīcāre, to entangle, perplex : in-, in; see IN-2 + trīcae, perplexities, wiles.]

perplexing vocabulary.com

adj

lacking clarity of meaning; causing confusion or perplexity

As in:

To illustrate the perplexing concept of anatman, the parable of
Nagasena and the King likens the mind to a chariot; a chariot is not a
pole, nor a wheel, it is the sum total of its parts.

Be careful -- in general I'm inclined to agree with "elusive", however it implies that the concept is likely to elude the reader -- which isn't the message that you want to convey (when explaining Dharma).

Remembering the advice attributed to Twain, i.e. ...

“Substitute 'damn' every time you're inclined to write 'very;' your editor will delete it and the writing will be just as it should be.”

... I'd recommend you don't use an adjective in that sentence, and say instead,

To illustrate the concept of anatman, the parable of Nagasena etc.

Also I think you're misquoting the parable slightly, or not paraphrasing it carefully.

There's an idiomatic phrase, "oft misunderstood", which might be applicable to what you're asking, i.e. meaning "difficult to understand". Perhaps that's professorial though, or something -- the word "oft" is archaic, so you might prefer "often", but "oft" can be used in this context.

Another word is subtle:

(especially of a change or distinction) so delicate or precise as to be difficult to analyse or describe.

"his language expresses rich and subtle meanings"

"Subtle" (and "deep") are used in this translation:

This principle I have discovered is deep, hard to see, hard to understand, peaceful, sublime, beyond the scope of reason, subtle, comprehensible to the astute.

The dictionary also suggests "difficult" but (again) that may be a turn-off, pedagogically speaking.

I like 'subtle' because it implies 'precise' (but dislike it because it implies 'slight').

Also I think that it's not difficult to explain (is it?), but only long -- there's a lot to explain. I wonder if there's a concise word for "tip of the iceberg" but I don't think so, so maybe rephrase the sentence as:

To begin to illustrate the concept of anatman, the parable of Nagasena etc.

I say it (i.e. the non-self doctrine) is "long" because I think it includes the following topics:

• What is "self" (or "Self"), i.e. atta or atman?


• What are the "five aggregates" (which aren't self)?


• Why is the non-self doctrine taught?


• What about the "person" (the subject Nagasena was discussing)?


• How is the non-self doctrine compatible with morality, karma, and social relations?


• What's the difference between non-self and death?


• What about pride, conceit? And possessions? What about "grasping" or "attachment"?


• How (if at all) does it relate to the doctrine on "emptiness" (sunyata)?


• What's significant about the phrase "in dependence on" (used in Nagasena's explanation)?


• How does that relate to nirvana (which is a.k.a. "the deathless")?

Instead of "long" it might be called "deep" (as above). Borrowing vocabulary from mathematics it could be called "non-trivial" i.e. "Not obvious or easy to prove" ... the opposite of "facile".

And an antonym of "facile" is "profound" -- so I suppose "profound" would be good adjective (echoing "deep").

The one problem with "profound" is pedagogical again -- i.e. not that it's an inaccurate description but that it sounds self-important or overblown.

So again, maybe no adjective is better.

"Important" might work, i.e. it might be true (it includes three meanings -- necessary, large, and valuable) and have a right effect on the audience; but I've read "important" described as a "dusty word" (which I think means overused, overgrown, overlooked, imprecise -- a placeholder for lack of a better word).

I think I'd recommend "fundamental":

• It implies "deep" and "profound" (both mentioned above)


• It implies "necessary" -- i.e. you must understand it, because it supports or informs subsequent doctrine


• It implies that what's being taught is "new", to the audience -- when you teach the fundamentals of a subject you're typically teaching a new subject, starting with the fundamentals


• It implies that this may be introductory explanation -- when something is fundamental you can expect subsequent explanations of what it's a fundament of.

It's also historically accurate, e.g. it matches the fact that the Anatta-lakkhana Sutta was one of the first suttas that the Buddha spoke, and, a doctrine which is said to be shared by all schools of Buddhism.

As for "difficult to understand" (rather than, to explain), some possibilities include:

• "Counter-intuitive" (assuming that most people naturally and 'intuitively' have a 'self-view')


• "New" or "novel" (assuming that whatever is new is difficult)


• "Paradoxical" or "seemingly paradoxical" (e.g. "What do you mean, 'non self'?! Who am I talking to then, and who is talking?"), however that sounds like criticism of it


• 
  

  Simply "difficult":

  
  
  

  
  

  "To illustrate the difficult concept of anatman, etc."

  
  

  
  
  

  That (wisely perhaps) says little about why it's difficult.

  
  
  

  Also it may be your best bet, e.g. if you're unclear whether you mean "difficult to explain" or "difficult to understand".

  
  

As I said though I'd beware of (I'd avoid) describing the dharma as difficult (because it's meant to be visible and 'inviting' and so on). I suppose that a teacher should (and that the Buddha did) match their explanation to the audience -- but I suppose that's harder when writing than in face to face dialog.

Also FYI I think it's canonically described as "difficult to explain" (or "to teach") rather than "difficult to understand" (see e.g. pratyekabuddha, and e.g. the udayi sutta) -- though also "hard to see" e.g. in MN 26 quoted above.

Another common word would be obscure

2. not readily understood or clearly expressed

It sounds like you are after something very specific in that the concept is difficult to comprehend not so much because it is complex or obscure but that it is abstract relative to common experience.

Equally you probably don't want to start introducing uncommon vocabulary when trying to explain an already difficult concept.

Personally I woudl use a word like difficult, challenging or abstract Presumably you are going to go on to explain the concept itself so a concise but obscure single word may be a bit redundant and unhelpful.

I would favour abstract is the literal meaning is pretty close and gets peopel thinking along the right lines while being a bit more positive than some synonym for difficult or complex.

abstract ADJECTIVE Pronunciation /ˈabstrakt/ 1Existing in thought or
as an idea but not having a physical or concrete existence.

‘abstract concepts such as love or beauty’ More example
sentencesSynonyms
1.1 Dealing with ideas rather than events. ‘the novel was too abstract and esoteric to sustain much attention’ More example sentencesSynonyms
1.2 Not based on a particular instance; theoretical. ‘we have been discussing the problem in a very abstract manner’ More example
sentencesSynonyms
1.3 (of a noun) denoting an idea, quality, or state rather than a concrete object.

To give more options to the already suggested ideas, let's dig up Oxford Thesaurus of English.

abstruse adjective

he was unable to follow the abstruse arguments put
forward: obscure, arcane, esoteric, little known, recherché, rarefied,
recondite, difficult, hard, puzzling, perplexing, enigmatic,
inscrutable, cryptic, Delphic, complex, complicated, involved,
over/above one's head, incomprehensible, unfathomable, impenetrable,
mysterious; rare involute, involuted. ANTONYMS clear, obvious.

---

convoluted adjective

an extraordinarily convoluted narrative: complicated, complex, involved, intricate, elaborate, impenetrable, serpentine,
labyrinthine, tortuous, tangled, Byzantine, Daedalian, Gordian;
confused, confusing, bewildering, baffling, puzzling, perplexing;
informal fiddly, plotty; rare involute. ANTONYMS simple,
straightforward.

---

intricate adjective

intricate Arabic patterns | the intricate
relationships between plants and animals: complex, complicated,
convoluted, tangled, entangled, ravelled, twisted, knotty, maze-like,
labyrinthine, winding, serpentine, circuitous, sinuous; elaborate,
ornate, detailed; Byzantine, Daedalian, Gordian, involved, mixed up,
difficult, hard; informal fiddly; rare involute, involuted.
ANTONYMS simple, straightforward.

Taking simpler options:

complicated adjective

the complicated election rules: complex,
intricate, involved, convoluted, tangled, elaborate, impenetrable,
knotty, tricky, thorny, serpentine, labyrinthine, tortuous,
cumbersome, Byzantine, Daedalian, Gordian; confused, confusing,
bewildering, baffling, puzzling, perplexing, difficult to understand,
above one's head; informal fiddly; rare involute, involuted. ANTONYMS
easy, simple, straightforward.

---

complex adjective

1 a complex situation | criminal law is an extremely complex
subject: complicated, involved, intricate, convoluted, tangled,
elaborate, serpentine, labyrinthine, tortuous, impenetrable,
Byzantine, Daedalian, Gordian; difficult, hard, knotty, tricky,
thorny, problematical; informal fiddly; rare involute, involuted.
ANTONYMS simple, straightforward. 2 a complex structure: compound,
composite, compounded, multiplex.

They are all suggesting similar words, but there are some fine differences. Lastly, let's switch sides!

straightforward adjective

1 the process was remarkably straightforward: uncomplicated, simple,
easy, effortless, painless, undemanding, unexacting; elementary, plain
sailing, a five-finger exercise, child's play; routine; informal as
easy as falling off a log, as easy as pie, as easy as ABC, a piece of
cake, a cinch, a snip, easy-peasy, no sweat, a doddle, money for old
rope, money for jam, kids' stuff, a breeze, a doss, a cakewalk; N.
Amer. informal duck soup, a snap; Austral./NZ informal a bludge, a
snack; S. African informal a piece of old tackle. ANTONYMS
complicated, difficult.

2 a straightforward man: honest, frank, candid, open, truthful,
sincere, on the level, honest-to-goodness; forthright, plain-speaking,
direct, unambiguous, straight from the shoulder, downright, not afraid
to call a spade a spade; informal upfront, on the square; N. Amer.
informal two-fisted, on the up and up; archaic free-spoken, round.
ANTONYMS evasive, guarded, disingenuous.