There are formed jhanas that have form: edges, colors, shapes, experiences that are distinct, well-differentiated, and rich in their features.
Formed jhanas can get progressively more refined, subtle, abstract, trending towards formlessness.
Various aspects of experience may disappear, body, sights, sounds, images, etc., and this may happen progressively, non-linearly, often fading, reappearing, fading, though, if we are inclined to formlessness, hopefully following a general, if meandering trend in that direction. So, in these experiences, we have a spectrum of formlessness, a formless that exists in shades of grey, a moving progression in the general direction of an ideal.
However, there are also formless realm experiences that arise that are much more dramatically clean in both the way that they arise and the way they present after arising that seem to be starkly delineated from the progressively more formless versions. They arise rapidly, sharply demarcated from what came before, and they present very much as advertised in the descriptions of the formless realms.
While one could think of even these two variants, that of shades of formlessness and stark formlessness in shades of grey, in that a formless experience can present more and more starkly, sharply, cleanly that some others.
Equally, one who has had the stark, sharp, clean, highly-formless, versions that fully meet the advertised ideal arise rapidly may think: no, there are two distinct modes, the softer progressive mode that is relatively formless but not truly formless, and the stark arising mode, and they seem very, very different.
I have at points held each of these views, typically arising depending on how recently I had the much cleaner version rapidly and sharply arise. My linguistic preference, however, is to be clear about which view you are holding at the very least. However, in my heart of hearts, I do feel that only the stark, categorically different presentation, that in which very refined versions of the formless realms arise in a strong shift, are the “true formless realms”, and everything else is something formed, however refined.
So, when describing experience and using the word “formless”, I advocate for adding additional words, qualifiers, and details such that people know what is actually being described rather than having to assume.
I use terms such as j3.j7, for example, to describe some third jhanic experience that really had very little form, space, or even consciousness in it but was still clearly third jhanic and not the extremely clean “true j7, Nothingness” that can also arise.
I might use the term j4.j6 to describe an experience that was much more fourth jhanic in its character but still had a significant aspect of vast, open presence, luminosity, and sense of all-pervading consciousness yet still had some form arising, however abstract, and so differentiate it from “true j6, Boundless Consciousness” in which form was utterly gone and it was like being in another realm of pure consciousness utterly removed in all obvious ways from the experiences of the space in which my body was sitting.
This is what is meant by “realm”, as in “The Six Realms”, as in somewhere and something else entirely, removed from the space in which we are practicing in the way that dreams and out of body experiences are.
Experiences at the level of a total shift in which realm we are experiencing represent strong meditative attainments. Often, we might get extremely short glimpses of such possibilities that last a mere fraction of a second. At other times, experiences of other realms can last many seconds, minutes, or even occasionally in very rare cases hours.
Most experiences of other realms are still formed and present with a diversity of features. However, a small proportion are truly formless and perform exactly as one would expect from the high descriptions of the formless realms, basically at the level of a Platonic Ideal but actually experienced.
Regarding the formless realms proper, those of the categorical variety, they very much tend to arise in strict sequence, shifting from j4 (the fourth jhana), to j5 (Boundless Space), j6 (Boundless Consciousness), j7 (Nothingness), to j8 (Neither Perception Nor Yet Non-Perception) and then out to the Post-8th Junction Point as I term it. Knowing this, if you have entered a state that has a lot of formless to it but doesn’t have that striking sense of utter detachment from your body and the space you are practicing in and didn’t arise in sequence, it is very likely of the dimensional version, some jX.jF (with X representing some jhana from 1-4 and F representing one of the Formless Realms from 5-8) variant, and not what I would term a true jF experience.
I don’t mean to disparage or downplay the value of formed jhanic experiences that have significant formless aspects, as such experiences can be powerful, profound, and even sometimes transformative, but I do wish to delineate that there are these seemingly categorically different experiences that truly do perform as “realms” and truly are “formless”, as well as experiences that clearly have some degree of formlessness and some degree of removal from ordinary consciousness and the space we are in.
By being able to think both dimensionally, that is, in terms of degrees and shades of grey, as well as categorically, that of a binary “true formless” or “some form remaining”, and by being very deliberate in how we express these modes of thought, we can be much better communicators as well as hopefully better practitioners.
Language that appreciates both the dimensional and categorical mode can help us to realize what might be possible and also how what we are experiencing might actually relate to those possibilities. It also helps avoid confusion when we speak and write about our experiences.
I hope this is helpful for your practice and for communicating about it with others.
Best wishes!
Daniel