The principle is simple, I will repeat it.
If you can think you must have a mind, no doubt about it.
Everything you experience happens in your mind.
IOW what you experience is not real, but a process in your mind.
Do you agree with the above?
No, actually I do not agree with those sentences in the way that you have phrased them, and I think that as I said much earlier in this thread, this looks very much like it's becoming a game of getting tangled up with words/semantics, just like so much of philosophy seems to descend into.
OK, so to explain what I disagree with in your above “principle” -
When you say “IOW what you experience is not real, but a process in your mind” … what do you actually mean by that word “experiencing”? … what is happening is that you have a sensory system that is exchanging electrochemical processes back and forth to the brain, and the brain is creating an impression of that very real input from the sensory system. That's what I think you are calling your “experience”.
But as far as any of us can honestly tell, that “experience” created by the functioning of the brain, is dependent entirely upon real input from a real sensory system which is detecting a real world around us.
The “experience” is a re-construction of the real world that is being detected by our sensory system. Afaik, if our sensory system never worked at all, i.e. if we had no sensory system, then the human brain would not be capable of producing any so-called thoughts or consciousness or “experience” of any kind. IOW – the so-called “experience” in your brain/mind, cannot appear for no reason at all and unconnected to any external reality … it only ever produces images, thoughts, feelings or “experiences” that are either direct representations of sensed reality, or else memorised examples of reality or imagination drawn from reality … afaik it's hard (perhaps impossible?) to even conceive of any “experiences” that are not connected in such a way to what our sensory system detects as “reality” … e.g., try to think of something that has no connection at all with anything you could ever have sensed as “reality” … I'm not sure you can ever do that?
So just to summarise that, in case the point is lost – when you say “what you experience is not real, but a process in your mind” … that does not mean that the events shown to you in your “experience” only take place in your mind. On the contrary the events themselves are the reality that is being detected by your sensory system … all that is happening in your brain in order to produce what you call your “experience”, is that the normal functioning of the brain is causing a rapid interchange of that detected information back-&-forth with the sensory system, so that it appears to us as if it is a continuous awareness, whereas in fact all that is happening is that information is rapidly updating and changing every microsecond, rather like running a long strip of still photographic images through a movie camera to make it appear like “real life”. IOW – it's an effect … what we “experience” as conscious imagery and sensations, is an effect produced by the brain rapidly and constantly processing sensory input.
Just to comment on your other two lines (for the sake of completeness) -
When you say “If you can think you must have a mind, no doubt about it” … no, actually I do not quite agree with that either. And I think we should all retain an element of doubt or skepticism about that. Just because something seems inescapably true, or seems to be “self evident”, we have learned in science, and even more clearly in maths, that you should avoid ever thinking thinking like that, as if to tell yourself that anything is a certainty without actual “proof”. In fact, the history of maths is littered with cases where in the middle of often very complex calculations, one seemingly certain thing was assumed to be true but without an actual “proof”, and where it later turned out that the calculations were wrong, it very often turned out that it was the seemingly “certain” assumption that was wrong.
However, in the present case I think this might be just another example of arguing about words, or of philosophical statements becoming misleading in their choice of words. That is - “if you can think”, then I agree something must be happening, but whether or not that means “you must have a mind”, depends on what you mean by a “mind”! … what science means by a “mind” is in effect the physical structure called your “brain” … as far as we can tell from all papers published in modern times by psychology, neuroscience and medicine … you cannot have a “mind” without the reality of a functioning brain. In fact afaik, you cannot have "consciousness, experiences, thoughts, a mind" etc. without a sensory system providing input to the brain.
OK, the last of your 3 points was to say “Everything you experience happens in your mind” … well again, No! Actually, not. You cannot say that everything you experience happens within your mind, because those “things” that you “experience” as thoughts in your mind, almost certainly all occur in reality outside of your mind/brain … what's happening in your mind/brain is only that you are re-creating an impression or sensation of that external reality. IOW I'm just saying that you need to be very careful in how you phrase any sentences like that – what you sense within your mind/brain as an experience of anything, does occur as a sensation within your "mind/brain”, but that does mean the events themselves are not happening outside of your mind in a real world, such that the only reason you are aware of any such events is simply because your sensory system is detecting those real events and causing the brain to create impressions of that external reality (the mentally created impressions are afaik, only ever just examples of inputs from vision, smell, hearing, touch etc. I.e., there are no other impressions or "experiences" except for those exact same sensations that are originally formed by the sensory system prior to any function of a brain/mind at all) … in fact, as we should all know, that is almost certainly what is happening … what you say are all “experiences in your mind” are simply rapidly updating sensations of reality being detected by your sensory system.