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?
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.
They're playing us like the Sims
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.