Comments and expansions
Experience itself is continually renewing itself. Simply rest at the edge of this waterfall.
This waterfall post reminds me of my most significant experience of a mystic state in an Ayahuasca ceremony: it was like a water-fountain where each particle of the fountain was literally "continually renewing itself", each particle coming into existence and going out of it.
Sam Harris "waterfall" metaphor is structurally identical to the "river" metaphor used by Daniel P Brown:
Before any concentration practice, the beginner is like someone drowning in the river of a distracted mind. The somewhat skilled practitioner begins to float by means of a supporting log held with concentration. Once accustomed to floating, the practitioner lets go of the supporting log and swims about in the very currents that previously threatened to drown him or her. At that point the practitioner swims with considerable skill, finally swimming to a calm, quiet shore. The practitioner can now see the entire stream, both its currents and its directions, from the perspective of letting it go its own way while remaining unaffected by it. (D.P. Brown & Thurman, 2006, p 262)
Varieties of comparing the mental event sequence to a flow of water
Sam Harris refers here to a core way the mind in meditation represents the flow of mental events to itself: as a flow.
In the traditional writings, there are several ways a long term meditator can experience the mind events occuring as a flow of water, once there is sufficient observational distance.
In particular the term mind "stream" is very important, as is, for example, the term "stream entry" (in Pali: sotapatanna)
The word sotāpanna literally means "one who entered (āpanna) the stream (sota), stream-enterer", after a metaphor which calls the noble eightfold path a stream which leads to a vast ocean, nibbāna. Entering the stream (sotāpatti) is the first of the four stages of enlightenment. (Wikipedia contributors, 2022e)
A dualistic view
This waterfall/river view is still a dualistic view: other than in the "ocean and mind" view, there is an observer and an external object (in this case the mind).
As Daniel P Brown points out (Daniel P Brown, 1981), there are different ways in which this "flow" can experienced, depending on the meditation tradition:
As continuous unbroken stream, like water
As a sequence of distinct mind-moments, like a stroboscopic experience.
Thus if for example, a novice meditator comes to meditation through Culadasa´s "The Mind Illuminated", the conceptual predisposition will be to experience the mind as a sequence of mind-moments. The theory of mind-moments is fundamental to Culadasa´s neuroscience-informed explanations. And, it is the one most in line with current science, for which "mind moments" is actually a valid concepts.
There is thus no "objective" flow in the mind. The experience of any type of flow is still an experience, and therefore, like everything else, constructed, even if it seems to be a reality.
My own experience of the water-fountain as sequence
My experience of the water-fountain in the Ayahuasca ceremony was more like a mind-moment perception: a sequence of very rapidly appearing and disappearing particles.
I had not started to meditate at that time, so it was an original "view", not influenced by any Buddhist meditation tradition.
Brown, Daniel P. (1981). Mahamudra Meditation-Stages and Contemporary Cognitive Psychology (Dissertation). http://abhidharma.ru/A/Tantra/Content/Raznoe/0028.pdf
This dissertation is a free download. It is a massive, highly technical volume that nevertheless gives an unparallelled insight into the education of a yogi.It draws on the knowledge of cognitive science as of the late 1970s, so it is not the newest in this regard.As compensation, Daniel P Brown gives some insight into the experiments with tachiscopy. to which he still referred in his retreats in 2021.The Universits of Chicago library entry:
Brown, D.P., & Thurman, R. (2006). Pointing Out the Great Way: The Stages of Meditation in the Mahamudra Tradition (Annotated). Wisdom Publications.
Gebel, Till. (2022l, September 15). My core mystic experiences with psychedelics and in meditation. Till Gebel. Retrieved 23 September 2022, from https://www.till-gebel.com/post/mystic-experiences-with-psychedelics-meditation
Wikipedia contributors. (2022e, September 8). Sotāpanna. Wikipedia. Retrieved 1 October 2022, from https://en.wikipedia.org/wiki/Sot%C4%81panna
Yates (Culadasa), J., & Immergut, M. (2017). The Mind Illuminated: A Complete Meditation Guide Integrating Buddhist Wisdom and Brain Science for Greater Mindfulness. Hay House Uk.