Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

What is reality?

  1. Sep 29, 2007 #1
    I need some help from Philosophy-oriented folk in answering this question, which I've been sounding off about in the Relativity forum in the thread "Raindrops and Gravity". After having a few of my deviant ideas ironed out there by people who know much more than I do, I've arrived at the following understanding:

    First, there is no need to doubt a bricklayer's view of "reality" in his immediate vicinity. He is likely to answer by hefting a brick, and tell you "that's what's real". And you'd better believe him.

    Second, you may describe this definition to a friend, and ask him to give you a more sophisticated example of reality. He could describe the new Ferrari he has over at his house, and tell you that it is "really" there. If you doubt him, you could go over and drive it around, if he'd let you.

    Third, if you ask a physicist whether a magnetic field is "real", he could try to convince you that it is by showing you iron filings sprinkled on paper above a magnet. You might then believe his claim.

    Fourth, you could approach an engineer who is building a machine to accelerate particles. He will tell you that Special Relativity (SR) requires him to take into account an increase in mass of the particles as they are accelerated. If you ask him whether this is "really" so, he would assure you that his pay cheque depended on his accepting that SR describes an observer-dependent reality.

    Fifth, you might ask a General Relativist if Spacetime, or the Riemann curvature tensor, were part of objective reality. He would insist that the latter is a geometric object in the former, that both are part of a four dimensional reality which is independent of any observer.

    Sixth. I don't know how a mathematician or a string theorist would define reality.

    I've arranged these "straw views" in increasing order of abstraction regarding a definition of reality. I don't which, if any of them are true. But my own conclusion is that in the end reality is nothing but a Platonic model in one's mind that matches, in as many ways as one can devise, the fullness of experience.

    I'd like to know if philosophers consider such simple-minded views on the subject.
  2. jcsd
  3. Sep 29, 2007 #2
    Whatever reality is, it is a collection of things that coexist. You look around and say that thing over there exists AND that thing also exists AND this thing over here exist, etc, etc. These coexisting things must not contradict each other but must support each other's existence. I should think that this should be the start of any derivation of physics.

    See the home page on my Public Profile page by clicking on Mike2 of this post.
  4. Sep 30, 2007 #3
    There seem to be two realities: One inside your your conscious brain--your mind, and one that is external to your mind. In the final analysis, only you can decide what are the realties you accept. Note: Sometimes that external reality can be really brutal and unforgiving. Note 2: Why ask the philosophers? They really do not 'know' what reality is any more than you do.
  5. Sep 30, 2007 #4
    True, but comments like yours are interesting and help to alleviate my ignorance. Thanks.

    The Comment Mike2 made:
    is indeed an essential ingredient of any model formulated to represent "reality"--- thanks also for this.
  6. Sep 30, 2007 #5
    Reality is that which Exists--it really is that simple--there is nothing else it can be.
  7. Sep 30, 2007 #6
    Right... and we say this thing "exists" AND that thing exists AND those things exist AND..... So all realtiy is a conjunction of facts. And this is equal to saying that no fact proves the nonexistence of any other fact. And this conjunction implies every fact implies every other fact. And this implication between facts has to be what is responsible for the laws of physics. For the laws of physics predict how one set of facts produces another set of facts. The resulting facts are caused by the initial facts. And cause and effect have the same relationship as premises implying the consequences. And there is no question that one set of facts implies another which imply a third which implies a forth, etc. And this is just like how dynamical laws of physics predict how facts propagate through time. So it must be that the dynamical laws of physics are derived from these paths of implication from one to the next to the next, etc.

    The question is how do we account for facts that we have not measured and are not aware of? Is there an infinite number of facts to account for? And what is the relation between facts and spacetime?
    Last edited: Sep 30, 2007
  8. Sep 30, 2007 #7
    Interesting questions. Let us define a fact as a thing given to the mind. Perhaps then we can say there are two types of facts (1) those facts that are metaphysically given via perception and (2) facts of reason via imagination. The first let us say are real and independent of humans, the second are abstract only within imagination thus not real until by volition made real. So, by definition, it is only the metaphysical facts that we need to account for, and we account for them via continued experience of that which exists. As to second question, I think there are only a finite number of metaphysical facts, but an infinite number of abstract facts, for, like the number line, you can always add in your imagination yet another abstract fact to any set of previous such facts, but of reality, existence cannot yet add anymore than it was given at origin of universe. As to third question, spacetime can be thought to be that which is intermediate between moments spatially separated--if so, then perhaps moments are the facts (either metaphysical or abstract) and the spacetime is the relation between them. Let me know where I error in thinking.
  9. Sep 30, 2007 #8
    I did not make a distinction between actual facts or what we humans preceive as facts when I said that facts much coexist in conjunction. I only meant to say if there were actual facts, then they must coexist in conjunction, not contradict each other, and in fact imply one another.

    That of course brings up the question as to whether this logical relationship between facts is actually real or just a human contrivance for our psychological stability. After all, there are no actual facts that are false in reality. False is only a human consideration of possible descriptions of reality. So is all of logic just a human contrivance? Or is there an actually real relationship of cause and effect between facts which would seem to suggest that facts imply each other? Our perception of the passage of time tells us that events proceed form one to another. And this suggests a cause and effect relationship so that there is an actual implication between facts. Or is time an illusion? We also think there was a beginning to the universe, a time when the universe was not, so that we can say that there was a state of non-existence where we can label existence as "false".

    General Relativity and Special Relativity designate each spacetime coordinate as an "event". This suggests that GR and SR labels each fact with spacetime parameters as you suggest. And perhaps separate spacetime coordinates are the only distinguishing thing between facts.
    Last edited: Sep 30, 2007
  10. Oct 1, 2007 #9
    Well, maybe. But it's a bit of a tautology, isn't it, since there is a temptation to then reply "that which exists is that which is real" ? However my dictionary agrees with you, so who am I to quibble...

    The distinction you made in your most recent post:

    looks at first sight pretty reasonable. But when one picks on specific examples in physics, the reasonableness seems to me to evaporate. Here is a chain of examples in which this becomes gradually more evident:

    A stick poked into water appears to be bent. We know that it isn't "really" bent because we can pull it out and check, and we can explain the bending because we understand the laws of refraction. Bending is a Type 1 fact?

    Hundreds of years ago Bradley discovered stellar aberration --- a small annually varying apparent angular displacement of stars of some seconds of arc . We understand how this is caused by our orbital motion. Another type 1 fact? But here a quite complex model of "reality", namely the Earth wheeling around the sun (distinct from our perception of the sun rising and setting), is imagined as part of "reality". It can of course be checked by other observations.

    We now believe that we, together with the solar system and Milky way, are moving at several hundred Km per sec relative to the reference frame defined by the Cosmic Background Radiation. This must produce an aberration of several minutes of arc, according to our present model of the cosmos (a type 2 "fact?). Yet we will never be able to directly measure this aberration, since it is fixed forever as far as we are concerned. Our existence is ephemeral on a cosmic scale. Is the assumed aberration itself a type 1 or type 2 fact?

    Then SR tells us that clocks on moving objects run slow. The observed extended lifetimes of relativistically moving radioactive particles confirms this as a fact. But is it of type1 or type 2? Again an imagined model of reality intrudes, but varies from observer to observer. Indeed, I believe that the essence of SR is this:
    And then there is the "reality" of spacetime and the Riemann. Definitely your type 2 fact?
    Or a very sophisticated and elaborate model in one's mind that is only a remote cousin of the bent stick in water.

    My conclusion is that your two categories of facts blur into different aspcts of some sort of accepted model of "reality" that we believe in if it is holomorphic with experience.
    Last edited: Oct 1, 2007
  11. Oct 1, 2007 #10
    By amplifying and extending our models of reality, which are very personal. For example , my model of reality doesn't include what you are doing at the moment, Mike2 (sleeping soundly, I hope).
    Only if the universe is infinite or infinitely complex. Nobody knows, I think.
    But is Spacetime real, or just a Platonic construct?
  12. Oct 1, 2007 #11
    Funny, I just started working on this:

    http://z13.invisionfree.com/Stabber_Palace/index.php?showtopic=1954 [Broken]
    Last edited by a moderator: May 3, 2017
  13. Oct 1, 2007 #12
    Plato thought that the 'idea of a thing' was more real than any kind of physical thing, which were only manifestations of their true essence. This is not quite the same as defining reality as being that which is in consciousness. For plato, the essences of things existed on a level separate from both the physical level and that of individual minds.

    I think this sort of thinking is really backwards. Mathematicians sometimes think this way when they talk about mathematical truths, as if you don't need a mind to come up with them. But how would we know this?

    The word "reality" has many definitions.

    I think the most simple definition of reality is that of consciousness. We don't really have a direct knowledge of what can be called physical reality. Its really just a metaphysical theory that explains why things appear in our consciousness and where our consciousness itself comes from. The only way to get empirical evidence is with our senses... it is impossible to transcend ourselves. Even with the instruments of science, we ultimately experience them through our senses. And this is true of people we consider wise, they teach us through our senses.

    If reality is more than we can experience, we don't know it.

    And really whether its a physical experience or a rational thought process, or a dream, its all part of consciousness, even if we categorize these things as different parts, or aspects of consciousness. Reality is consciousness. The cause of reality is unknown, and probably unknowable with any real degree of certainty.
  14. Oct 1, 2007 #13
    However, when one realizes that one cannot voluntarily stop beathing for more than a few minutes, one begins to realizes that there is, lurking outside of one's consciousness, something much more powerful than mere consciousness. Whether we call it reality or something else, it is primary, and without it there is no consciouness.
  15. Oct 1, 2007 #14
    No, all one needs for this is a gun a single bullet. And neither the gun, nor the bullet need be outside consciousness, assuming one does it oneself.
    One can certainly posit an external cause for consciousness, but that begs the infinite regression question, at what point is there a first cause. Consciousness could be its own first cause. We really have no way of knowing, although its a good assumption ontologically, its still an assumption in the epistemological sense.
  16. Oct 1, 2007 #15
    The breath holding example was used so one could remain alive to appreciate the experience of how easy it is for something to overcome the conscious human will.

    The example of oxygen was to point out that human consciousness requires oxygen to sustain itself. I think that no reasonable person would assert that human consciousness predates the existence of oxygen

    The real, primary reality, is the matter/energy that composes and supports human consciousness. Human consciousness is the secondary reality that allows us to experience the primary (because it must exist first) reality of matter/energy.

    As always, the individual has the final say as to what they accept as real... at least as long as they keep breathing.
  17. Oct 1, 2007 #16
    You are missing the point entirely.

    We don't experience oxygen. We experience breathing. If you don't understand that there is a difference here, then you are not understanding a very basic philosophical argument.

    'Oxygen' is a conclusion based on observation, but the observation is a primary aspect of consciousness, whether its a dream, a thought or sensory experience.

    What is primary, is that I sense things and I can relate those things together within my consciousness. An understanding of how atoms combine into oxygen and how the body uses oxygen is something you were told, or read about. That is, its something that you have in your consciousness, but you don't experience directly. Where did that understanding come from? Where did your consciousness come from? You can't even concieve of 'oxygen' until you are, and unless you are conscious, so consciousness is primary.

    One can theorize about what happened before one is conscious as well as when one sleeps.... but it requires assumptions and connecting dots. Its not part of our reality in any direct way.
  18. Oct 1, 2007 #17
    You might consider that without oxygen, human consciousness is not even possible. But, then, we would not know this unless we were conscious. But if the oxygen was not there first, there would never be any human consciousness to be primary.

    OK, you say human consciousness is primary and I'll say oxygen is primary (because I believe it was there first) and then at least one of us be might be right.
  19. Oct 2, 2007 #18
    Its not a matter of what you believe. I'm quite confident we need oxygen to exist. That is simply not the point. Consciousness is primary because we need to have it first before we can even think about oxygen. Oxygen may exist in the ontological sense, it surely does, but when discussing consciousness and reality, one has to address the epistemological as well.

    Your oxygen example is ignoring the question of consciousness, not addressing.
  20. Oct 2, 2007 #19
    My dictionary lists 19 definitions/usages of the word primary, so maybe we are not talking about the same 'primary'. Everytime someone drowns, it is obvious that lack of oxygen trumps human consciousness.

    No one knows for sure exactly what is human consciousness, but there is compelling evidence that without matter/energy there are no humans or human consciousness.

    Knowing what is reality is not an argument that anyone wins. So if I do not get your point, it does not matter at all. I have my own reality just as you have yours. Thanks for the discussion.
  21. Oct 2, 2007 #20
    Yes, but I think it better to start a philosophy from a tautology than a contradiction, for if reality is that which does not exist, we spend lots of time thinking about nothing. But a way out is to follow this sequence from axiom (1) existence exists, (2) reality is "that" which exists, (3) how do I know if something is real ?...--thus your reply not needed, existence priori to reality by axiom.

    No, in this example bending no type of fact at all--bending perception an illusion.

    Nice example, but the only type 1 fact I can find in what Bradley discovered is that the earth moves.

    I would argue that if in fact the mental assumption can never be tested, the best you would have is a type 2 fact. To move a type 2 to a type 1 fact the contents of the imagination must be transformed back into metaphysical reality, which is the source of the type 1 fact. But recall, that the ultimate source of content of the type 2 fact are sets of type 1 facts rearranged.

    Clearly the experimental results from SR provide type 1 facts. All perception of the metaphysically given by definition varies from observer to observer, but this does not negate that each observer does not perceive a type 1 fact. Consider this example, let C = an event metaphysically given, that clock runs slow. Let A = observer 1, B = observer 2. Then the type 1 fact given via perception to the first observer is the set [C+A], and to the second observer [C+B]. But neither [C+A] nor [C+B] are developed within the imagination, they are presented to the imagination for it to use if it so wishes.

    Both examples of type 2 facts.

    If by blur you mean they (the two types of facts) form a dialectic to assist the mind to provide explanations of reality that are consistent with experience, then I would agree with you. Again, I offered that reality is that which exists. To help the mind explain what is real and what is not one can use facts. But I suggest there are two pathways (1) use facts that are directly metaphysically given (2) use facts that recombine the first types of facts into new facts within imagination then back transform these new facts into metaphysical facts by testing the predictions the second type of facts hold to be true. So yes, there is a blur in my suggestion, but is not this "fact" blur the essence of Einstein method of deriving Theory of General Relativity ? The blur is the synthesis of the dialectic of the metaphysically given and the reason of imagination, which we call creativity. Thanks for a nice thread.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook