OP, you have it right, that is, your understanding of what is being said is correct.
This was something the intellectuals actively struggled with in the 19th century. In this view, all matter including the world and every single thing in, it including you and me , formed a big clock which wound up at the time of the Big Bang a few billion years ago.
After that Big Bang, the laws of physics have completely determined what has happened and will continue to completely determine what will happen. This determinism extends to all all events including your own thoughts at any given time and every decision you’ve ever made or will make. What has happened anywhere could not have been any different from what it was given the initial conditions of matter and energy and the laws of physics.
That’s about as stark and plain a representation of this POV as can be formulated.
Perhaps most physical scientists buy into this view. It was revolutionary and sophisticated in the 19th century, but there are rebuttals available to us today that they could not have availed themselves of. I made my quasi-rebuttal here just a few days ago here:
From a sociological POV I would say there’s now a complete split between lay people and physical (physics, chemistry biology) scientists. Other scientists don’t seem to ponder it or hold strongly definite opinions on the topic. (source: me)
Intellectuals and artists still actively take up the issue and have strong feelings about freewill/ determinism. For instance, Kubrick’s “A Clockwork Orange” (and the book it was taken from) is all about just this issue. The question there is “are people’s actions and characters determined.. are people a kind of organic clock…. a clockwork orange (orange as in fruit) ? “
You can see how Kubrick treated this idea in the context of the then prevailing BF Skinnerian notions of operant conditioning and the rejection of cognition as causally potent (or even real).
I read Harris as a sort of throwback to this view, albeit he is not rejecting thought itself as Skinner did. For Harris people still think, but the agency implied by that activity is denied and dismissed as an illusion.
Wikipedia will quickly tell you everything you need to know about BF Skinner if you aren’t familiar with his theories. Essentially, Skinner said all outward behaviour was a result of conditioning by the outside world and not the result of any kind of thought or reflection or inner processing. Such things were casually impotent epiphenomena at most. Skinner weirdly thought they were actually non-existent.
I remember my first year cog sci instructor introducing us to the concept of algorithm by giving us a certain hard puzzle to solve- the Towers of Hanoi (details unimportant). After we spent some time messing around trying to solve it, he told us how to think about the problem so as to find a solution. It was easy after that.
“There”, he said, “that’s sort of a mini refutation of BF Skinner and behaiourism” and in fact it was just that.
Most cognitive scientists now view Skinner as having been just run-of-the-mill wrong. The whole thing was just weird from the start. He denied you had thoughts (yes, he did) . Yet you know you have them through introspection. So who are you going to believe, Skinner or your lying eyes?
Another sociological note. I know people from the time when BF Skinner ruled the roost (inside joke intended). His POV became a kind of “party purity test” wherein if you did not subscribe, you were subtly viewed as just unable to accept the hard truth about people; you were too weak to let go of your old fashioned comfort-producing notions that you had a meaningful inner life inside your head.
I see much the same thing with the freewill debate now . Determinism was revolutionary cutting edge thinking- 150 years ago. There’s reasonable room for other interpretations of reality not because determinism isn’t a correct description of reality but because today we are more comfortable with the idea that the very basics of how we construct reality- time, space, causality, little particles effecting each other etc etc -and by implication all phenomena -may just be one limited aspect of something we can’t or haven’t grasped yet.
Of course, if we don’t know anything about it, then “it” can’t be used as the basis of an argument for or against anything, including freewill except in the very vague and universal sense in which things may ALWAYS be different than our current theories have them. The thing is, this very general asterisk at the bottom of every theory is interesting in this context. There’s something f Pascal’s wager at work here. What do you lose if you believe you have no free will and it effects you in a very bad way and then it turns out later that we were just wrong about the whole way we conceptualized the problem and “something like” freewill does in fact exist. It’s not like nothing is at stake here, is it?