Deeply seeing into and experiencing the interconnectedness of all of existence is a precondition for genuine compassion. Even if one has a philosophical or conceptual understanding of the interconnectedness of life, it is not enough to generate true compassion. Why is this?
Without the direct and deeply profound experience of oneness, we can never actually feel for others. It is the actual feeling of oneness that is the basis of feelings for others. It is a felt experience, not an idea, image, or concept.
Ordinarily, deep seated awareness and natural feeling for others is obfuscated; i.e, clouded over, by our entanglement with fixed notions of "how the world functions." Part of the problem is due to our use of language; the medium of intellect and communication which is structured by the core assumption of separateness and the existence of fixed entities. The Dalai Lama described this rather succinctly when he said:
"The view of the world as made up of solid objects with inherent properties is reinforced further by our language of subjects and predicates which is structured with substantive nouns and adjectives on the one hand and active verbs on the other."
Without ongoing meditative practice (zazen) it is difficult, if not impossible, to defuse the effects of language and its power to continuously reinforce the notion of fixed entities, events, structures, etc.
It is only when all our fixed ideas and concepts about the "nature of reality" are completely let go of that the experience of the interconnectedness of all of life can be directly realized along with the emergence of true love and compassion for all beings, including ourselves.
Zazen is a razor sharp sword for cutting away the stranglehold that language has on our ability to let go of fixed ideas. The more that we practice zazen, the easier it becomes to see the provisional "reality" that is built into the very structure of language itself. The reality that we "think of" and in turn, construct, becomes less important than the direct experience of reality that is beyond the ability of language to describe.
"Regard all dharmas as dreams," is a gentle reminder for us to not get caught up or hung up by verbal descriptions of reality. They are by their very nature limited and incomplete so it's OK for us to let go of them, over and over and over again. Just hold them lightly and then release them, like a freshly caught trout, and keep to "not knowing" as often as possible. Our very own inherent love and compassion, which is none other than the basis of the interconnectedness of all of creation, will manifest.
It is then that we can truly be of service to others empowered by the love we feel for ourselves. To the degree that we clearly see that "self love" equals "universal love" are we able to be of service to others.