In reply to Coel Hellier:
> > But if you don't know what they are and when they were formed, ...
> I do know what they are (I can just ask myself), and I do have a rough idea of how they formed, over decades.
Is all your knowledge so articulatable? Do you know how your brain can learn to see round a new floater in your eye? How do you know, vis a vis, your persistent complaint of child indoctrination with religion, that those early thoughts, you only have a rough idea about, aren't more intransigent than you believe.
> > ... are your sure there are no biases inherent in those early constructs determinative of all later choices about what reality is?
> As I said just above, no I can't be sure that I have no biases so pervasive that they can't be overcome, all I (and we) can do is do our best. How do we do our best? We recognise that humans are prone to bias, and so only trust ourselves if we can get external corroboration. The insistence on double-blind medical trials is a good example of recognising that we are prone to biases and of doing our best to overcome them.
Okay, doing our best is a fair expression of pragmatism. I'm happy with that, but such a humble attitude to one's own origin of beliefs doesn't give a very secure pulpit to preach about the errors of those who believe in God. So will you now desist?
> What is notable about religious believers is that they shy away from accepting such biases, and place great store in mere intuition and feeling, and indeed actively veer *away* from rigorous checking for bias, and actively embrace practices and attitudes that enhance bias.
No. They place great store in experience, but are not so doctrinaire as to presuppose and shove down the throats of others one "materialist" view of reality. I assert that the biases are on the other foot. We are kindly reminded by our atheist friends with regular monotony the probability of our biases, and Christian's themselves believe religion is a bias that can usurp God by placing an idol in God's place. Rather, materialism is a self fulfilling prophecy. The rigorous checking of bias is really the rigorous entrenchment of intransigent materialism, the a priori ruling out of any novelty. Thus we have the phenomenon of Kuhn's paradigm shifts, and Tegmark's deliberate Jekyl and Hyde approach to the publication of his mathematical reality ideas, so as to preserve what might otherwise have been a very short career indeed. No, your "checking" isn't to remove bias, it iss to entrench it and secure a conservative inflexible system.
> > Can you give an example of any large shifts in your beliefs about existence.
> Yes: in the past I would have considered the concept of causally disconnected universes to be sensible; now I don't really.
I would say that is tinkering at the speculative edges.
> > And we still have a fundamental problem with the lack of explanatory power inherent in your
> > definition of "existence" in that it shows no justification for the presence of an objective
> > existence, and yet we believe it, do we not?
> > Is Tegmark right that: "If a reality exists independently of us, it must be free from the language that
> > we use to describe it. There should be no human baggage. In which case how can we know objective
> > reality except always from a limited distance?
> A mere *definition* is not even supposed to be an account of human psychology and of why we have the feelings that we do. Nor is the definition of "existence" an account of all the evidence that might lead us to whatever conclusions. All it is is a criterion for qualification for the set "exists". You are still placing great store on your primary intuition about "exists", and are holding that out as an infallible standard that my definition is held up to. I simply don't accept that premise. Now provide your evidence that your primary intuition is reliable.
> Yes, Tegmark is right. But can I once again emphasize the distinction between (1) what exists, and (2) what humans can know about what exists. The answer to your last question is "we can't". What *humans* can know will always involve human limitations. I reject your idea of an infallible, intuitive, "direct-line" to reality.
A definition is a parsimonious expression of the meaning of a word. You need not make an account of psychology, but if you cannot express all that the word means succinctly without recourse to psychological accounts, you should back down on your claim that all words are definable, except perhaps in an a priori impoverished and inadequate sense. Thus, you must also admit there there are some words that are not properly definable. What is the meaning of the word "existence". You don't really believe it is "anything that has chains of causal links back to our sense data", because that necessarily excludes the idea of existence being objective, and necessitates its subjectivity, and I honestly don't think that we see reality like that. Perhaps Tegmark is right, and physical reality is just an expression of maths. In many senses, such a notion of physical reality is truly illusory, the universe fooling kindly fooling itself, and I don't see that as being any better a situation than solipsism.
Whatever the case, what you are expressing now reveals two fundamental problems: one, we can only "do our best" with regard to what could be essential biases, and two, that there is an essential inadequacy of language to deal with the idea of objectivity. This puts great pressure on the idea of any knowledge being anything more than illusory does it not, and sense data doesn't necessarily help undo that problem if there is not way to securely express it. I suggest you don't reject the idea of an intuitive connection with reality, you are proposing and backing it in the conservatism of your intransigent materialism.
> > And yet we do know it?
> Do we know, infallibly, about external reality? No, we don't. Humans are not infallible.
Well, I wouldn't have gone for infallibility, that is *your* word. But I wouldn't go for the opposite either, that such intuitive, and unexpressable knowledge, as you so adequately demonstrate, is necessarily suspect. And frankly, that isn't the way we live, as is evidenced by our free use of language, and words such as "existence".
> > What are those thoughts about reality that lead us to think it really is objective?
> The whole of evidence about the natural world. As I've said, the "external world existing regardless of us" scenario has far more explanatory and predictive power than any alternative. For example it explains why we think the things we do.
But it doesn't "explain" anything, it describes it and transfers what we sense into what you amply show is inadequate language. Consistency is rather a reflection of our explanatory bias, the self fulfilling prophecy of our predetermined axiomatic views. Furthermore, the use of the word "existing" as you have defined it in quotation marks above is truly absurd as it represents a very real contradiction in terms, undone, by your explicit, but impoverished definition.