I have heard from numerous sources that our senses cannot be relied upon and therefore all knowledge that we have is subjective & relative. In other words, many people claim that variance in perception implies variance in concepts that a person forms/deduces.

Yet, I know that color blind people accept the same physics as we do.

Doesn't this mean it may be possible to have concepts which are objective?

Other questions: OR perhaps if you think color blind people subscribe to the beliefs of the majority, does that mean if 50 million Frenchmen think gravity is unreal then so will it be? Or if you think that the beliefs of the majority are infallible why do you think lynching ought to be prevented?

  • This feels off-topic (and a bit rambling/undirected) to me as currently formulated. I would encourage you to clarify your context and theoretical concerns as much as possible, and keep in mind the site is not a philosophy forum.
    – Joseph Weissman
    Aug 5, 2011 at 12:49
  • Only the final question is really a philosphical one. The rest is developmental learning which would be off topic.
    – Chad
    Aug 5, 2011 at 19:23

1 Answer 1


Your numerous sources are wrong. Senses can be relied upon to a large extent (fortunately). Otherwise you would have been unable to write your question. Also, you can verify colors--that a flower is yellow, for example--by taking it around to other people and asking them what color the flower is. If you observe a high degree of agreement without them knowing in advance what the answer was supposed to be, then you can deduce that, although you are unable to directly perceive that quality of the object, there is some quality that others are perceiving in a consistent way.

If you read a bit about the philosophy of science, you'll perhaps begin to see how this works (especially in the case of things we can't sense, like the quantum spin of nuclei--but MRI machines work consistently, don't they?).

It has much more to do with consistency than with beliefs. If everyone thinks the long-haired stranger should be lynched, you conclude not that the long-haired stranger should be lynched, but that there is some feature of the long-haired stranger that the locals consistently find deserving of lynching.

  • I'm pretty sure what he is referring to in his first sentence is Humean skepticism and/or Kant's noumena/phenomena distinction (which he asked about in a previous question). In this regard, he is absolutely correct; our senses tell us nothing truly objective about the world. They are very subjective and very relative.
    – stoicfury
    Aug 6, 2011 at 4:44
  • @stoicfury - Whether it is "subjective and very relative" depends on one's theory of knowledge. Given how much more subjective and relative things could be (and are not), I'm pretty happy calling widespread agreement of sense-input "objective". I agree that senses do not construct formal proofs for us from irrefutable premises.
    – Rex Kerr
    Aug 7, 2011 at 1:20
  • Asking other people isn't necessary. Just look at the wavelength of the reflected light which can be measured and put into categories such as invisible colors, e.g. ultraviolet and infrared. Colorblind people just have a few colors more they cannot see, yet still could measure.
    – k0pernikus
    Jan 7, 2013 at 19:49
  • @k0pernikus - You still need to know what that wavelength is called, which you have to do by consensus again. And it is by observing consistency that we know that wavelength is a property of light that correlates with perceived color (and energy of the photon).
    – Rex Kerr
    Jan 7, 2013 at 20:18
  • @k0pernikus - speaking as someone who suffers from red-green confusion, I was about to make your very point about UV and IR, but you beat me to it so I'll have to settle for explaining that we see the full spectrum but the dynamic response range of our sensors overlaps too much making it hard for us to discriminate colours that are near in frequency. So red or green LEDs are both fine for indicate power on, but if you use a change from red to green to indicate that charging is complete, it makes me want to choke you with the power cord. Make it flash when it's finished.
    – Peter Wone
    Dec 12, 2015 at 4:44

Not the answer you're looking for? Browse other questions tagged or ask your own question.