Wherefore dreams ?

Why do we see total strangers in our dreams? Are they people who crossed our lives and evoked in us strong feelings of affection or fear or disdain? And then we somehow forgot about them.

Why do we dream of strange situations? Are they our secret desires surfacing, our suppressed fears, our hidden fantasies?

What messages are they trying to tell us? Or are we just housecleaning? Are dreams messengers from our subconscious mind or a subconscious vacuum cleaner?