How do you know that dreams aren't reality and reality's not a dream?

It's something I've been thinking about.

My dreams have been so vivid here. I'm frequently confused of my surroundings when I awake and later may wonder whether a memory was real or a dream. My life is bleeding between the dimensions.

I welcome dreams of my family, because it's as if we're not on opposite sides of the earth. I see them so clearly, even the facial expressions and the empathy, it's uncanny. One of the books I was reading was questioning our assumption that dreams are not reality. I do wonder. Is it possible that we are actually connecting with people in our dreams? Can dreams become reality? It seems so.

I wonder again if "Row your boat" really is what it's all about.