The world of physics cannot condemn the world of everyday experience as illusory without so condemning itself

Every one of us must of heard someone contend that the world of our everyday experience is an "illusion," or something similar, and that physics proves this is so.

Here is a typical example: "Quantum physics tells us that reality is far beyond human perception and intuition. In other words, our rational mind and common sense are just not capable of understanding the true nature of reality."

Or here: "The world around us is real, yes, but it is not what we perceive it to be."

There is plenty more of this around. The problem with it is that the very same manuever that condemns the world of everyday experience as illusory completely undermines physics itself, and so the very basis for this argument. Why? Because every single finding of physics ultimately rests upon someone's perception of everyday reality. No matter how sophisticated are the instruments we (think! aren't the instruments part of this "illusion" as well?) we have devised, ultimately a human being has to read their output, and incorporate it into a theory so it becomes a "finding of physics."

But if I can't trust my perception of the chair I am sitting on as I write this, how can I trust my reading of a voltmeter? How can I even know that what I am looking at is "really" a voltmeter? If the tree in my front yard is not at all what it seems to be, then my spectrometer is also not at all what it seems to be. If my impression that the wall in front of me is solid is illusory, then my reading of the manometer in front of me is probably similarly illusory.

One dodge that might try to avoid the force of this argument is noting that physics, in some sense, "works." This dodge is an obvious failure, as the world of everyday perception overwhelming "works" as well: it got the human species through 100,000 years of history before the invention of physics quite successfully. In fact, in deciding whether to attempt to run through the wall before me in order to leave this building, if I have to choose between the common-sense view that it is solid, and the "debunking" of this understanding by subatomic physics,  I will choose common sense, thank you. (The idea that physics has shown the wall "really isn't" solid relies on equivocating between different meanings of solid in the first place.)

Note: This post is not "anti-physics": I have good reason to trust the findings of physics, because I trust the everyday perceptions upon which those finding are based.


  1. "One dodge that might try to avoid the force of this argument is noting that physics, in some sense, 'works.'"

    I absolutely ****ing hate it when scientists or engineers pull this. It is so obviously bad, but they use it anyway, implying that talking about reality has to do with getting something to run.

  2. I dislike the "sense data" move in philosophy because it just invites moving in this direction, as if our senses and what they receive are not also part of the world. Once one starting talking about "sense data" one has already created a conceptual gulf which seems almost designed to block clear thinking.

  3. I definitely like the spirit of what you're saying here, Gene, but to plug a hole in your armor: What if someone says, "Hang on Callahan, did you just 'prove' that illusions don't exist, period? I mean, if I can't trust my eyes in the desert when I think I see water, how can I trust me eyes when I read in a book that it talks about 'mirages'?"

    1. Channeling Ayn Rand: it's not your sensory data is faulty, it's that your processing of it is faulty.

  4. In a sense, the "our rational mind and common sense are just not capable of understanding the true nature of reality" crack is making the same point you are, though in a more confused (or disingenuous, depending on how generous you are) way.

    A more accurate statement would be that extrapolating our everyday experience to scales and realms with which we have no experience can lead us astray. Our everyday experience with walls and baseballs led humans to posit that the building blocks of matter must be tiny hard spheres or blocks. But of course this is an abstraction and an extrapolation from a scale at which it makes sense to a completely different scale with which we have no direct experience, so it shouldn't be completely shocking that physics actually tells us that atoms are mostly vacuum.

  5. You should read some Nils Bohr. I think you will like what he has to say. He makes some similar arguments.