Sometimes I dream that I write and on waking up I find it is untrue and that I have been dreaming.
Now I am writing this post.
How can I be certain now that this activity is not being done while asleep?
This action of writing now may be a dream and I may wake up.
This is a problem not solved by Philosophy.
Hinduism describes four states of Being.
Jagrat, the waking state.
Swapna, the dreaming state,