What is most real to the individual is the individual has thoughts and via the Theory of Mind, other human individuals also has similar thoughts. Humans will have spontaneous thoughts or thoughts that are triggered by some mental processes.
You cannot jump [as in in OP] to imply there is a
reality out there that humans interact with.
The question is how sure are you that what is manifested in terms of thoughts and images in the brain represent a real reality out there.
Based on research, it is claimed;
Your Brain Hallucinates Your Conscious Reality
Thus what a norma person thinks and cognized [see, feel, etc.] as real is at best a more "realistic" hallucination in contrast to a hallucination in the brain of a schizophrenic.
The fact is the brain is triggered by electro-magnetic waves from somewhere and an image and sense of reality is cognized.
It is very difficult to prove there is an absolute independent reality out there, as Russell [early] claimed "perhaps there is no [real] table at all
" but merely a cluster of particles or waves.
The fact is the human brain has inherited certain inherent instincts and concepts via evolution. With thoughts coming from somewhere, the brain will structure certain images and sense of reality to the best of its abilities. At times, the brain will deceive the conscious mind if it has to.
Note this two-normal face illusion experiment;
A normal person [as you are] if uninformed of the deception will see two normal faces but that is a lie the conscious brain has presented to the mind.
There are hundreds of example where such illusions and lies are presented to the mind as real.
Now with the above example and proof, how can you be sure what you think and perceived as real in normal perspective is actually really real and not a lie and deception by the brain.
The truth is Your Brain Hallucinates Your Conscious Reality
to facilitate survival of the individual and the species. Such hallucinations come a continuum of reality from the real of the normal person to the unreal of the schizophrenic.