What if I'm asleep in a hospital somewhere and I could die any moment they decide to pull the plug?!?! 
Jesus why has my mind been giving me existential crisises at night this week? 
What if I'm asleep in a hospital somewhere and I could die any moment they decide to pull the plug?!?!
Jesus why has my mind been giving me existential crisises at night this week?
The human brain doesn't have the capabilities of synthesizing the richness of life de novo. Dreams and hallucinations are transitory and ephemeral things. Longitudinal consistency makes the idea of such a long-term hallucination absurdly implausible.
Oh thank god that makes sense
Incidentally, this is why liberalism exists. /s
What if it's not a human brain that's dreaming?
That's true... it could be a techbro:
We can only really think in terms of likelihoods. Why would a non-human super-organism, who had the mental capacity to simulate the external universe with such consistency and fidelity, dream up such a human life?
It's all a fun reasoning puzzle of course. We don't really fear that we're dreaming, we fear that we're awake and that this is what life is.
I don't think I've ever had a dream wherein I was not human, but I have had dreams about interacting with Martians and My Little Ponies.
They're playing us like the Sims