Everything we know is relational. Everything we understand is alone due to relations, differences. One cannot establish whether they are cold if they have never experienced heat. As a result of a lack of juxtaposition, we may confuse ‘cold’ with being normal temperature. This applies to all aspects of life. One cannot experience happiness without experiencing sadness. Once we have established an opposition on the spectrum, we can create comparisons that enable us to define the world around us.

Based on this understanding, lightness is only perceived as such when darkness is experienced:

                 Spoiler: this video looks like a snippet from a paranormal activity scene