“The Zohar states that a kiss is the merging of one breath with another. Love begins with the physical attraction. Then, as lovers begin communication, they begin to speak. As they get closer, they stop speaking and are merely aware of each other’s breath. Finally, they come closer still, and their communication becomes a kiss, at which point they are actually in physical contact. At this moment, in the kiss, they are aware of each other’’s life force. Kissing is thus a natural consequence of increased intimacy in speech. The two mouths come closer and progress from speech, to breath, to the kiss. Thus there are four levels in the intimacy of love: physical attraction. speech, breath, and the kiss. These same levels exist in the relationship of a person with the Divine.
This level corresponds to a still higher level of the soul, even above neshamah. This fourth level of the soul is known as chayyah, which literally means ‘life force.’ If the level of neshamah involves an awareness of the breath of the Divine, then the level of chayyah is the awareness of the divine life force itself.”

– Rabbi Aryeh Kaplan: Introduction to Kabbalah, Meditation and Prophecy