Eckhart Tolle: A New Earth p. 217
"As without, So Within
When you look up at the clear sky at night, you may easily realize a truth at once utterly simple and extraordinarily profound. What is it that you see? The moon, planets, stars, and luminous band of the Milky Way, perhaps a comet or even the neighboring Andromeda Galaxy two million light years away. Yes, but if you simplify even more, what do you see? Objects floating in space. So what does the universe consist of? Objects and space.
If you don't become speechless when looking out into space on a clear night, you are not really looking, not aware of the totality of what is there. You are probably only looking at objects and perhaps seeking to name them. If you have ever experienced a sense of awe when looking into space, perhaps even felt a deep reverence in the face of this incomprehensible mystery, it means you must have relinquished for a moment your desire to explain and label and have become aware not only of the objects in space but of the infinite depth of space itself. You must have become still enough inside to notice the vastness in which these countless worlds exist. The feeling of awe is not derived from the fact that there are billions of worlds out there, but the depth that contains them all.
You cannot see space, of course, nor can you hear, touch, taste, or smell it, so how do you even know it exists? This logical-sounding question already contains a fundamental error. The essence of space is no-thingness, so it doesn't "exist" in the normal sense of the word. Only things--forms--exist. Even calling it space can be misleading because by naming it, you make it into an object.
Let us put it like this: There is something within you that has an affinity with space; that is why you can be aware of it. Aware of it? That's not totally true either because how can you be aware of space if there is nothing there to be aware of?
The answer is both simple and profound. When you are aware of space, you are not really aware of anything, except awareness itself--the inner space of consciousness. Through you, the universe is becoming aware of itself!
When the eye finds nothing to see, that no-thingness is perceived as space. When the ear finds nothing to hear, that no-thingness is perceived as stillness. When the sense, which are designed to perceive form, meet an absence of form, the formless consciousness that lies behind perception and makes all perception, all experience, possible, is no longer obscured by form. When you contemplate the unfathomable depth of space or listen to the silence in the early hours just before sunrise, something within you resonates with it as if in recognition. You then sense the vast depth of space as your own depth, and you know that precious stillness that has no form to be more deeply who you are than any of the things that make up the content of your life.
The Upanishads, the ancient scriptures of India, point to the same truth with these words:

What cannot be seen with the eye, but that whereby the eye can see; know that alone to be Brahman the Spirit and not what people here adore. What cannot be heard with the ear but that whereby the ear can hear: know that alone to be Brahman the Spirit and not what people here adore....What cannot be thought with the mind, but that whereby the mind can think: know that alone to be Brahman the Spirit and not what people here adore.