See nondualism.

https://en.wikipedia.org/wiki/Nondualism

It's considered an "ultimate truth" in those traditions. The question isn't whether or not this is delusional, it's why is this experience widely shared across human history.

Judging from the page description they make the same mistake of simply ignoring definitions and coming up with their own.

Is there anything special to this experience? Historically, all kinds of delusions were "widely shared". This is true even today. People "talked" to trees everywhere around the world.

> Is there anything special to this experience?

Yes, it is plausible, but logically impossible.

What do you mean by "impossible"? I just described exactly how people get that experience: they mess up definitions. It is a perfectly logical description.

Under influence people think peeing in public is OK is plausible, though logically it is not the best action to take. So that is not unique either.

Use the concept of paradoxes in Taoism as a metaphor for nondualism:

> The paradox is that by talking about the Tao, and by attempting to define the Tao, we ensure that the reader does not actually grasp the concept. At its heart, the Tao is nonverbal in its essence, beyond the confines of language. The Tao is an experience rather than definition.

Each tradition has their own version. For the west, it's the coincidentia oppositorum of Nicholas of Cusa. This goes beyond definitions because language can't describe it. This is not a failing, this is the essence of its impossibility.

What you just described makes about as much sense as Seado - a word that I just came up with - e.g. no sense at all.

You're starting to get it. Paradoxes, contradictions, and nonsense is how these traditions attempt to get the practitioner to overcome dualism. The problem is that you think you can use either-or logic to understand it when the practice is designed to destroy it.

Get what? Understand what? Destroy what?

Dualistic thinking.

As I explained above, what you call "dualistic thinking" is just refusal to follow common definitions for relatively simple concepts. For example, Wikipedia's entry for abovementioned personhood is clear enough to say, that I and you are two distinct persons. The two of us may be called a person, but it has nothing to do with the "way of thinking", and only has to do with the definition of a person. If a definition of a person had a clause, that would prevent congregates of persons to be a person, no amount of "dualistic thinking" would make two of us, or the entire humanity a person.

Sadly, this discussion appears to be at an end. Nondualistic thought processes are not based on definitions. They are based on direct experience of the ineffable, beyond words themselves. You keep trying to impose Aristotelian logic on to paradoxes, contradictions, and nonsensical attempts to break one out of dualistic perceptions. There are numerous ways this works, from dreaming, to creativity, to peak and flow experiences of all kinds, all of which aim to break the mind out of what is perceived as separate and to give it a new holistic POV. Just as you cannot have music without the notes that define it, you also cannot have the notes without the empty spaces between them. You can pretend that the notes represent the music, but it is also equally composed by its absence in the form of silence. They are one and the same.

There's nothing ineffable in anything you are referring to. Anyone can generate tons of bullshit by combining letters and words. You are clearly much worse at Seado than I am at non-dualism. Your thought process needs to grow much before you can realize significance of Seado. Then you will learn some truth (and still it will not be universal).