Help me that way I'll waste no more time.

[Grey Acumen]

actually it has to do with the fact that a silhouette is exactly the same from the front and the back, so there are always 2 ways to interpret any nondefined image. further more, the third dimension can only be extrapolated from visual cues on a 2 dimensional media, since our only cue is that movement is happening, but no shaodows or lines or features tell us anything more, we are left open on which direction to extrapolate.