How do physicists know that an external world exists?

[fractalzen]

TL;DR Summary

Since our perceptions are always transduced into nerve impulses, and we can ONLY know these impulses, how do you know that the external world even exists? And why would physicists assume it does? Tradition?

We know that whatever we experience as happening in the universe is actually a model created in our brains. For example when we look at the Milky Way Galaxy, light rays are transduced in the rods and cones into nerve impulses and we experience those impulses and not the actually light from the Milky Way. In fact the physics tells us that the whole panorama of the night sky and its feeling of vastness is all completely contained in the brain within our skull. [This begs the question-- do the photons which gave rise to the nerve impulses also only exist in our brains/minds, leading to the conclusion that everything is 'mind', for lack of a better word? And if so, why are there two different sides to our 'minds'--the light and our transduced perceptions of it, and does this have something to do with the right brain/left brain split and/or quantum decoherence? What is a dream and is there a dream property to the universe? Admittedly these are speculative.] Still, my question remains How do you know an external world exists, and why would you assume it does?

 

[Vanadium 50]

First, this is philosophy, not science.
Second, this is lousy philosophy.

 

[PeterDonis]

my question remains How do you know an external world exists, and why would you assume it does?

As far as physics is concerned, the answer is that our physical theories are built on the assumption that an external world exists, and they work--they make accurate predictions. That's all that physics can do.

If you want more than that, you're asking a philosophy question, not a physics question.

 

[PeterDonis]

Since the OP question is really philosophy, not physics, this thread is closed.