Stanford Encyclopedia : Perception
Wikipedia : Direct and Indirect Realism
On various philosophy forums I've participated on, there have been arguments between those who call themselves 'direct realists' and those who call themselves 'indirect realists'. The question is apparently about perception. Do we experience reality directly, or do we experience it indirectly?
When I was first initiated to the conversation, I immediately took the indirect side -- There is a ball, photons bounce off the ball, the frequency of those photons is changed by some properties of the ball, the photons hit my retina activating light-sensitive cells, those cells send signals to my brain communicating that they were activated, the signals make it to the visual cortex and...you know...some stuff happens, and I experience the sight of a ball.
So, my first thought in the conversation about Indirect vs Direct realism was that there was a lot of stuff in between the ball and my experience of it, so, it must be indirect.
But then I found that direct realists don't actually disagree about any part of that sequence of events I described above. For them as well, at least the few that have bothered to respond, photons bounce off a ball, interact with our retinas, send signals to the brain, etc. The physical process is apparently the same for both sides of the debate.
And when two sides vehemently disagree on something, and then when the question is broken down into easy, answerable questions you find that they actually agree on every relevant question, that tends to be a pretty good hint that it's a wrong question.
So, is this a wrong question? Is this just a debate about definitions? Is it a semantic argument, or is there a meaningful difference between Direct and Indirect Realism? In the paraphrased words of Eliezer, "Is there any way-the-world-could-be—any state of affairs—that corresponds to Direct Realism being true, or Indirect Realism being true?"
I tend to think this is the wrong question.
Here's roughly what happens: there are various signals (light, air waves, particulates in the air) that humans have the capacity to detect and translate into neural states which can then be acted on. This is useful because the generation, presence, and redirection of these signals is affected by other objects in the world. So a human can not only detect objects that generate these signals, it can also detect how other objects around it are affected by these signals, granting information that the human brain can then act upon.
All of this is occurring in reality: the brain's neural firings, the signals and their detection, the objects that generate and are affected by the signals. There is no "outside reality" that the human is looking in from.
If you break it down into other questions, you get sensible answers:
"Does the human brain have the capacity to gain information from the ball without a medium?" No.
"Is the human brain's information about the ball physically co-located with some area of the brain itself?" Sure.
"Is the signal detected by the sense-organs co-located with some area of the brain itself?" Potentially at certain points of interaction, but not for its entire history, no.
"What about the neural activity?" That's co-located with the brain.
"So are you trying to say you are only 'Directly acquainted' with the signal at the point where it interacts with your sense-organ?" I don't think calling it 'directly acquainted' picks out any particular property. If you are asking if it is co-located with some portion of my brain, the answer is no. If you are asking if it is causing a physical reaction in some sensory organ, the answer is yes.
'Breaking it down into other questions' is exactly what needed to be done. I agree. And once it is broken down, the question is dissolved.