When two people kiss each other on the cheek or forehead it is an action that verifies one’s affection towards another and communicates a certain level of unity.
The essence of love and affection is to unite.
Kissing lip-to-lip represents even a closer union between two people. In order to kiss on the lips two people have to get really close to each other. This closeness of two faces in the act of kissing represents and expresses a closeness of two hearts. In kissing, the bodily act corresponds to the act of the mind and will.
Kissing on the lips is a form of profound communication by one’s inner spirit to unite with another’s inner spirit. In other words, kissing goes deeper than the physical meeting between two people’s lips. Kissing touches the heart and mind. In kissing, we have the desires of two people to blend.
The eyes and mouth are real mirrors of the soul. Nothing communicates sadness or happiness in a person faster than the eyes and lips.
The human race has the most “fleshy” and expressive lips in the entire animal kingdom. The reason for this is that we humans have evolved to communicate our affections on a deeper, spiritual level. Human lips have adapted their structure and physiology to express the more complex subtleties of the human psyche. Scripture even makes use of kissing to express a unity between qualities of mind that other animal species cannot acknowledge or perceive.
Mercy and truth are met together; righteousness and peace have kissed each other. (Psalms of David 85:10)
So in a way, kissing offers some visceral evidence of a human soul and the existence of a loving God in heaven.