As a Buddhist, I would look to the Hebrew scriptures for the purpose of comparative religion. Due to the limitations of human language, are the various world religions explaining the same Ultimate Truth in diverse ways?
Much like the Hindu scriptures distinguish between Brahman with attributes (relative truth) and Brahman without attributes (Ultimate Truth), the Tao Te Ching distinguishes between the nameless Tao and the named:
The Tao that can be told is not the eternal Tao;
The name that can be named is not the eternal name.
The nameless is the beginning of heaven and earth.
The named is the mother of ten thousand things.
Ever desireless, one can see the mystery.
Ever desiring, one can see the manifestations.
These two spring from the same source but differ in name;
this appears as darkness.
Darkness within darkness.
The gate to all mystery.
The named Tao and the nameless Tao spring from the same ultimate source. The Tao would be entirely unknowable to limited beings such as ourselves without the use of human language, however inadequate it might be.
Please compare the above quote from the Tao Te Ching to the following words of Shinran Shonin:
The Supreme Buddha is formless, and because of being formless is called Suchness. The Buddha, when appearing with form, is not called the Supreme Nirvana. In order to make us realize that the true Buddha is formless, it is expressly called Amida Buddha; so I have been taught. Amida Buddha is the medium (relative truth) through which we are made to realize Suchness (Ultimate Truth).
Amida Buddha and the formless Dharmakaya spring from the same source, but differ in name. Without the name and form of Amida Buddha, the Ultimate Truth of Dharma-body would be inaccessible to unenlightened beings.
Like the Buddhist concept of Dharma-body or Buddha-nature, Taoism teaches that the Ultimate Reality is inseparable from our original nature, our True Self:
“Master,” the disciple asked, “what exactly is the true self?”
The sage replied, “Ultimately, your true self is the Tao and the Tao is you.”
“I find that hard to believe, Master. The Tao is great; I am insignificant. The Tao is powerful; I have but a little strength. The Tao is unlimited; I labor under many limitations. The Tao is everywhere; I can only be in one place at a time. As far as I can tell, the Tao and I are completely different. How can you say that I am ultimately the Tao and the Tao is me?”
Rather than to respond directly, the sage handed the disciple a bowl: “Go to the nearby river with this and use it to bring back some water, then we’ll continue the discussion.”
The disciple carried out the order, but when he came back, the sage looked at the bowl and frowned. “Didn’t I tell you to fetch the water from the river? This can’t be it.”
“But it is, Master,” the disciple was confused by the disapproval. “I collected the water by dipping the bowl into the river. I assure you that this water absolutely is from the river.”
“I know the river quite well,” the sage said. “All kinds of fish swim in it, but I don’t see any fish in this water. Numerous animals come to the river to drink from it, and yet I see no animals in this bowl. Many children from the village frolic in the shallows of the river. Well, I see no children here either. Therefore, this cannot be the water from the river.”
“Master, it is only a small amount of water, of course it cannot contain all those things!”
“Oh, I see,” said the sage. “Well, in that case, I want you to go pour the water back into the river.”
The disciple did so with a puzzled expression on his face. He couldn’t help but wonder what had possessed the sage to act so strangely. He completed his task and returned.
“Is the water back in the river?” the sage asked. The disciple nodded.
“Good,” said the sage. “That small amount of water you brought back is now the same water that touches the fish, the animals and the children. In fact, everything that the river is now applies to the water we were both looking at just a while ago.
“Think of the river as the Tao and the water in the bowl as your true self. From a limited point of view, that water seems very different from the river. It is understandable how one can be led to believe that the two are not the same and can never be the same. The river is far greater than the bowl of water, just as the Tao is far greater than an individual human being.
"Having carried water from the river, you can now see it from an expanded perspective. The river is the source of the water, just as the Tao is the source of our true inner selves.”…
The water must return to the river. Even if the water isn’t poured back, but spilled somewhere, it will still flow or seep its way into the river. Similarly, when the body is no longer a suitable vessel, the true self it contains must return to the source. Religious people may call this source God; atheists may call it the laws of nature; we call it the Tao. Whatever its label, it is our point of origin as well as our ultimate destination.
Just as the water becomes one with the river, the true self merges with the Tao. That’s when we realize that the feelings of isolation and separation are illusory. You and I are never truly isolated or separated from the divine source of universal creation. We are never truly alone. Oneness, the Tao that unifies all, is the ultimate reality… of the true self.
There was something formless and perfect
before the universe was born.
It is serene. Empty.
Infinite. Eternally present.
It is the mother of the universe.
For lack of a better name,
I call it the Tao.
It flows through all things,
inside and outside, and returns
to the origin of all things.
The Tao is great.
The universe is great.
Earth is great.
Man is great.
These are the four great powers.
Man follows the earth.
Earth follows the universe.
The universe follows the Tao.
The Tao follows only itself.
Much like Hinduism teaches that Atman is Brahman, Mahayana Buddhism teaches that one’s own Buddha-nature is the Dharmakaya. Universal Buddhahood is our True Self.
The crux of Zen is to awaken to the Original Face, and one who has done so is a buddha. Any external Buddha or God we seek, entrust ourselves to, or believe in, falls short of the true buddha. Zen proclaims that the true buddha is nothing other than the self that has awakened to our Original Face.