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I think that’s overly reductionist, but ultimately yes. The human brain is amazingly complex, and evolution isn’t directed but keeps going with whatever works well enough, so there’s going to be incredible breadth in human experience and cognition across everyone in the world and throughout history. You’ll never get two people thinking exactly the same way because of the shear size of that possibility space, despite there having been over 100 billion people to have lived in history and today.
That being said, “what works” does set constraints on what is possible with the brain, and evolution went with the brain because it solves a bunch of practical problems that enhanced the survivability of the creatures that possessed it. So there are bounds to cognition, and there are common patterns and structures that shape cognition because of the aforementioned problems they solved.
Thoughts that initially reflect reality but that can be expanded in unrealistic ways to explore the space of possibilities that an individual can effect in the world around them has clear survival benefits. Thoughts that spring from nothing and that relate in no way to anything real strike me as not useful at best and at worst disruptive to what the brain is otherwise doing. Thinking in that perspective more, given the powerful levels of pattern recognition in the brain, I wonder if creation of “100% original thoughts” would result in something like schizophrenia, where the brain’s pattern recognition systems are reinterpreting (and misinterpreting) internal signals as sensory signals of external stimuli.
Ah, I think I misread your statement of “followers by nature” as “followers of nature.” I’m not really willing to ascribe personality traits like “follower” or “leader” or “independent” or “critical thinker” to humanity as a whole based on the discussion I’ve laid out here. Again, the possibility space of cognition is bounded, but unimaginatively large. What we can think may be limited to a reflection of nature, but the possible permutations that can be made of that reflection are more than we could explore in the lifetime of the universe. I wouldn’t really use this as justification for or against any particular moral framework.