If reality is just hallucination, how come different people see same objects I wanted to ask this question for a long time but couldnt find any thing to support my argument. Today i found this https://www.ted.com/talk/anil_seth_how_your_brain_hallucinates_your_conscious_reality#t-694887, where the speaker Anil seth  theoretize that our reality is just a hallucination. Exchange of information happens both ways inside and outside, i.e, we not only perceive the world around us but also actively generates it. 

Perception is an active constructive process. To summarise, 

Hallucination is uncontrolled perception, then 
Perception is controlled hallucination.  

My question is, If thats the case then how two people would agree on the same state of world?
According to Anil Seth, in this talk, consciousness is an active construction process. In that view, for the subject to have an experience about world, physical signals from mind independent objects are processed by brain and a highly probabilistic mental content of the physical is experienced. Even though I mentioned objects, it could be material things and features.
But our sensory abilities are not inherently cable of perceiving everything. The range of vision is 360-400 to 760-830nm. Similarly, for audition its 20Hz to 20,000Hz. There are other phenomena like aftereffects and adaptations, which too work along with perception. The information thus processed by sensory faculty is further compared with prior data that is stored in the brain and brain tries to come up with a decent construction of mind-independent objects. This experience can be called a controlled hallucination as there are other possibilities for such construction.
The general organization and working pattern of typically developing humans brains are very similar, especially in the early processing of sensory signals. Similarly, the physical signals that it processes of mind-independent objects are also very similar. Given these two, it is highly likely that two people have similar experience, even though we cannot confirm it and can only say that we share a human like experience.
Reference:

https://plato.stanford.edu/entries/perception-problem/

https://en.m.wikipedia.org/wiki/Constructive_perception

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2888317/

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4763133/