I saw your post some time ago, but as I’ve been away on retreat and so on, I just now got around to responding. Sometimes it takes a while for my addled old brain to digest things and see something useful to say.
In my oft-misbegotten youth, my friends and I would from time to time use a float tank, so I have some idea of the kind of experience they offer. But that was way before I started meditating, so I haven’t meditated in a float tank, nor can I directly compare the experiences, I can just compare meditation with my memory of a float tank.
Floating was a lovely experience. There was nothing like a process or intentional path: just get in and see what happens. Much of the time in the tank is probably spent hovering back and forth on the boundaries of sleep. It didn’t feel like a particularly expansive or transformative state of consciousness, but it was pleasant, and afterwards there was a gentle and peaceful sense, almost a tingle of aliveness.
I don’t believe, however, that we can really compare this directly with meditation per se. And I came to realize that the key problem was the use of the word “deprivation”. Deep meditation is not a state of being “deprived” from the senses, but of being “freed” from them.
Let me say, I reject utterly the distinction between so-called “Visuddhimagga” and “sutta” jhanas. It is unsound scholarship. The distinction has a passive-aggressive ring to it, pretending at scholarly grounding yet hiding a clear value-judgement, subtly dismissive as it claims to illuminate. This is not how scholarship should be done; and to be clear, it is not something that I would acknowledge as meaningful scholarship or research at all. We would all be better off had this false distinction never been made.
As far as I’m concerned, there are just jhanas as taught by the Buddha and the Buddhist traditions. In the last few years, a few teachers and practitioners in western Buddhism, having caught up with the idea that jhanas are actually a thing—which we have been teaching for decades—describe some of the initial steps on the way to deep meditation as if they were jhanas. The states they describe are familiar to an experienced meditator. They are part of the journey, yet there are also states that lie well beyond their ken. For jhanas are deep and profound, they are the very doorstep to nibbana. The sages of old gave up everything, retreating to the forests and mountains for decades to practice them, often trying and failing. It is of these elusive and profound, subtle states of transformed consciousness that I speak. I have written and spoken extensively on this topic, so I will not repeat all that here, but will focus on trying to frame a response to your question.
The senses are suffering. O, how much suffering! Sights are a pain, an impulsion, a striking of noise on the eye. The eye, the physical organ, is so supremely sensitive, it expands and contracts to let in light or keep it out, adjusting for vast differences in the quantity of light, coping with the glare of a sunny Australian beach and able to detect even just two photons when fully dark-adjusted. So sensitive is the eye! All that information must be sorted, processed, recognized, at a tremendous cost to the brain. Think of how vast the processing power it takes a modern computer to process images and run neural nets, just badly and coaresly recognize a few patterns in a photo. We do far more, with extreme precision and accuracy, every moment, without even being aware. And the sight is just the beginning! Each sense is an impact, a striking, a harsh and irrefusable demand by the outer world. Our sense mechanisms are digesting and making sense of all this, passing the information over to the brain, where our mental model of the world starts to be constructed and continually updated.
So for all our attachment to, and hungry pursuit of, pleasures of the senses, it is still a blessed relief to be freed from them. To step into a quiet forest, to plunge under the ocean surface, or even to sink into a float tank, all give at least a degree of relief, a slowing and quieting of the flow and demand of sensory load.
The experience of deepening in meditation is the pleasure and relief of freedom from these senses. Even in ordinary states of mind, we speak of being “immersed” in a good book or a reverie. Our senses can be relatively neglected, and as our focus sinks into what we love, we lose awareness of what is around. Notice that even at this shallow level, there is a distinct difference between the experience of trying to concentrate on a book, which will never result in immersion, and losing oneself in a book that one loves.
It should go without saying that here, as with every aspect of the mental cultivation of transformative consciousness, the terms we use to describe everyday states of mind have but a coarse and approximate relation with the realities that manifest in the process of meditation. For these things, there simply is no common shared experience upon which to build a well-understood vocabulary, so we must rely on metaphorical stretching of everyday terminology.
The experience of freedom from the senses is not deprivation, but fulfillment. Released from the tugging and pulling, the poking and the prodding of the damn senses and their pain, at last there is peace. Think of how sensitive the eye and other senses are: then know that the mind is infinitely more so. It is so unspeakably tender and gentle, like a baby, prodded by the needles and probes of sense experience.
If we think of deep meditation as a state of “deprivation” it makes sense to think of what is envisaged in that state as a “hallucination”, that is, as a false simulacrum of reality, concocted by the mind to make up for the sense experience from which it is deprived. But if the experience is one of wholeness and fulfillment, of a blissful immersion in light and joy, then we need a different way of talking about these things.
The suttas do not use the word nimitta to mean a light seen in meditation (as I pointed out in my first book, A Swift Pair of Messengers). Rather, nimitta in the context of meditation, means “an aspect or quality of experience that, when focused on or brought to awareness, tends to promote the growth of similar or related qualities”. The use of the word nimitta especially for the preliminary development of the light in meditation was introduced, or at least popularized, by the Visuddhimagga, and should not be back-read into the suttas.
The use of terms denoting “light” and “radiance”, etc. is pervasive in the suttas when speaking of such profound states of stillness. Indeed, as I have pointed out elsewhere, the very words jhāna and samādhi both have a sense of “light” to them, and might be translated as, say, “illumination” and “incandescence” rather than “absorption” and “immersion”. Other words like obhāsa, pabhassara, pariyodāta and so on are constantly used in the context of jhana. And in many places similes of light are used quite explicitly as well.
The mind is the knowing. It is awareness. The nature of the mind is to know, but normally much of its energies are taken up with the task of lesser knowing: that is, accepting and making sense of the masses of information that flow through the senses. This is essential for survival in this realm, but it takes its toll. But when freed from this constant stream of impacts, the mind flowers open, tender and joyous, relaxed and gentle, free at last. No longer cowering and protecting itself from whatever might strike it, it has trust and clarity. Finally it can “know” in a better, deeper, higher way. It is ready for insight.
For a meditator, it is practically useful to find a place of peace and quiet, to help set the scene and get them on their way. Especially as the mind is starting to become quiet, any sound or other impression can readily jolt one back to awareness.
In principle, perhaps it may be the case that the deeper sensory quiet of a float tank can help with this process even further. Perhaps; and ultimately that would be a matter for a meditator to find out for themselves. However, I suspect that for most it may be too much of a good thing. A certain degree of physical alertness is required, and a little discomfort tends to stimulate the mind, avoiding drifting off to sleep. Even sitting in overly-comfy chairs often leads to a more drifty and sleepy meditation; there is a reason why the cross-legged posture is preferred. Even for those such as myself, whose knees prohibit extended cross-legged sitting, a simple chair is better than a sofa.
In the end, I think the float tank will, like most modern spiritual innovations, be found to serve a convenient purpose to help some people find a degree of peace and solace. But lacking a meaningful grounding in the overall development of a spiritual path, I fear the benefits will be quickly exhausted, and one who relies overly-much on such specialized crutches will find themselves looking for something more substantial.