Is it expression if there's no one around to see it?

This is similiar to the question, "If a tree falls in the forest and there's no one around to hear it, does it make a sound?"
So consider this, can expression exist if there is no one around to express it to? Does expression have to be interpreted by another for it to in-fact be expression?

Here are the various definitions of expression -
ex·pres·sion Pronunciation (k-sprshn)
n.
1. The act of expressing, conveying, or representing in words, art, music, or movement; a manifestation: an expression of rural values.
2. Something that expresses or communicates: Let this plaque serve as an expression of our esteem.
3. Mathematics A symbol or combination of symbols that represents a quantity or a relationship between quantities.
4. The manner in which one expresses oneself, especially in speaking, depicting, or performing.
5. A particular word or phrase: "an old Yankee expression . . . 'Stand up and be counted'" Charles Kuralt.
6. The outward manifestation of a mood or a disposition: My tears are an expression of my grief.
7. A facial aspect or a look that conveys a special feeling: an expression of scorn.
8. The act of pressing or squeezing out.
9. Genetics The act or process of expressing a gene.

We had this discussion in my Literature class the other day and it got pretty heated, I was just wondering what everyone else thought. :-)