Reflections and Windowpanes

Seeing myself in the glass, I wonder what existence qualifies as. My double doesn't speak, think, or act, but I do, and it is me. Thus it does and does not exist. Do I really exist, then, if this transparent version of myself does? Do you really exist if you think you do, or do you only exist because you think you do? Do I really exist, or am I the reflection in the windowpane?