A person feels a phenomenon solely from the opposite state. For example, we cannot see the light unless there is something that reflects it. We cannot see in complete darkness if there is not at least some source of light. The more opposing properties, sensations and knowledge a person combines in himself, the more developed he is. In Kabbalah, this is manifested in the growth of egoism - the opposite of the Creator's property - bestowal. And the more egoism a person has, the more he wants to devour everyone and everything, the higher he rises up the spiritual steps by adding to this growing egoism the correct intention - for the sake of bestowal.