How we perceive

Traces of a roe (little deer) in the concrete
of a cycle track

Philosophers often come with new theories which then are refuted by other philosophers with again new theories. Such theories are about all kinds of themes: ethical and moral theories about what we should do, theories about the best political system, theories about the essence of man, theories about how we act (my specialty), theories about being, theories about happiness, and so on. I could make here a long, if not very long list of philosophical theories, but you know what I mean. And, of course, philosophers discuss, and sometimes fight as well, what the best theory in their field is. But how do we know what the best theories are? How do we know which theories are true? Philosophical discussions are mainly discussions about ideas, not about facts. By nature, philosophical theories just are about what cannot be experienced or at least not directly, and because of this they cannot be tested. In the end, philosophical ideas are mere speculations; they are views – albeit reasoned views – on how the world is constituted. They are subjective. We can also say that philosophy is about what is not empirical.
Therefore it’s a pleasure when we find facts that maybe don’t prove philosophical views – for that’s not possible – but that at least make some theories quite likely and in a sense give them a kind of empirical foundation. Take for instance the way we look at the world. A view long sustained by many is that what we see around us is passively received in the brain via the senses, especially by the eyes and ears. The world we see leaves a kind of imprint somewhere in the brain, like in the memory, just as a stamp that you push in a soft substance like wax; or, to take a modern metaphor, like how a printer prints the image on your computer screen on a piece of paper. This view is called naïve realism. However, as empirical research has made clear, it works in a very different manner. In a way, perceiving is more a brain-to-world process than a world-to-brain process, although the latter certainly plays an important part. I’ll spare you the details how it really works but basically it is so that we first make a construction in the brain how the world around us is and then we test this construction with the information that comes to us through the senses. With the help of this incoming information the constructed “image” in the brain is improved. To know this as a philosopher is very interesting, especially if you are an epistemologist, for in fact it confirms two philosophical theories. As Gerhard Roth makes clear in his Aus Sicht des Gehirns (= From the Brain’s View Point), pp. 86-87: Thinking is the most important organ for perception. Starting from genetically determined interpretations or interpretations required in early life, each process of perception or observation is a kind of making hypotheses about forms, relations and meanings in the world. To put it differently: The way that processes of perception and observation articulate our environment in meaningful forms and events is the consequence of trial and error; of trials to make constructions and interpretations that are then tested and improved. It is a matter of confirmation and correction. Is this not exactly Karl Popper’s well-known scheme P1 > T1 > E > T2 > P2 as discussed, for example in my blog dated 13 July 2015? Is this not Karl Popper’s theory that scientific theories are developed by putting forward an idea, then testing it and then correcting it with the help of the test results as summarized in this scheme?
This way how the brain forms an image of the world is, so Roth continues, also exactly the way it is stated in the field of knowledge theory by the adherents of the idea of epistemological constructivism. This view says that there is no direct representational connection in the brain of what happens in the world and the contents of our perceptions and observations. To put it crudely, there is not a kind of photo of the world around us in the brain. What happens in the world stimulates our senses and these stimulations are the basis of the processes that construct our conscious perceptions and observations, so what we think to “see”. In this way there is no independent knowledge of the world (so there is no “photo”), but for us our knowledge of the world is what these brain-made constructions are. These constructions are continuously tested with the help of new information coming from the outside in the Popperian way just mentioned. However, the brain as such cannot distinguish between its own constructions and the world outside. For the brain the world outside is the construction it has made.
Although philosophical theories are non-empirical, when developing and discussing their views, philosophers can learn a lot from what empirical research has brought. 

Source
Gerhard Roth, Aus Sicht des Gehirns. Frankfurt am Main: Suhrkamp, 2015.