We know that consciousness is a projection of the brain, it is highly rational to presume that it ends when the the brain is no longer functional.
It is highly irrational to believe that we carry on dreaming after we die since even when you are asleep your brain’s neurons are firing to project the conscious experience of your dream.
Just because two things are not known for certain doesn’t mean that they are equally believable. You don’t know for 100% certainty whether you will be alive or dead tomorrow, but you do know it is more likely that you will be alive than you won’t be.
We don't
know that consciousness is a brain projection. We
believe that is, based on neuroscience, which is grounded in physicalism.
Phenomenologically, the mechanisms are still unknown. The hard problem remains unsolved.
Rational deduction is the only means we have for discerning what is true and what isnt, if you choose to ignore it as a means to seek truth then you are basically acting as in the same way as the bluepilled.
This is philosophically and demonstrably false. Rationality is a very useful tool to help us reach truth, but it's not the gold standard. There are some truths that can be deduced
a priori, but there are many truths that are reached
a posteriori, such as through empirical observation (mostly reliable) or personal (mostly dubious). Some epistemologists argue that even empirical observation is merely an approximation of truth, though a very good one in an overwhelming number of cases.
Suppose that you and I both have never observed or experienced fire or its effects. All we have are other people's accounts of what it is and how it is. So we sit for hours, day after day pondering and arguing for what it means for something to be "heated" or "burning." We can build beautiful logical arguments and structures that seem to give us the truths about fire. But the absolute best way to learn the truths of fire in this case is to simply light a torch, bring it close to your hand, then throw it on something combustible. We then deliberate and comtemplate the implications of this, or simply start playing around with fire.
Truth can also be reached experientially, though we require a more delicate treament of experience as a means or avenue of reaching truth. One way to know what "blue" is like is to see the color for yourself. I can show you fMRI scans of people seeing blue and show you physics experiments that have measured the wavelength of blue, but it does absolutely nothing for you in the quest to understand what the truth of the experience of seeing the color blue really is. You, as the scientist looking at the data of blue versus the conscious experiencer of blue will have two completely different truths, both of which happen to be the subset of "the truth of blue" (let's call this B), but there's no edge that connects the child nodes of B with each other in the graph.
Rationality has a very obvious wall here that it cannot climb nor otherwise circumvent. It has hard limits, as does empiricism (but that's a slight tangent). Rationality does a good job of closing certain gaps to reach truth in a way that can be easily traced, but even the best builders cannot build a house with just one tool.
