"We human beings are amphibians.
We live in two worlds: the material and the spiritual, and sometimes on the borderline between them.
We are aware of the differences, just as the difference between dry land and water is clear even to the smallest frog.
However, although we jump continuously from one existence to the other, we are often unaware of the jump.
Although we live in two worlds, one of them seems to be the real world, the real existence, while the other seems much more hazy, not quite as real.
We smell scents and hear sounds, and our sense of sight is our main way of understanding the world, but the ultimate way in which we verify the existence of things is by touching them.
We equate real with tangible.
Things that we cannot grasp in our hands are less real to us.
Although we know—either from books or from direct experience—that most things, even in the physical-material world, cannot be perceived through our senses (from radioactive rays to microscopic germs), still, this does not change our strong, primitive notion that reality is that which we can sense.
Because we can touch it, the material world is real.
In a different way, we are also participants in another, nonmaterial world.
This abstract, nontangible world is certainly not in the same category of reality, yet it is no less real."
Just as we inhabit the material world, we also exist in a spiritual world.
Since such "spirituality" seems to range from wishy-washy to clinically crazy, it is not at all astonishing that some people keep a safe distance.
All these are intangible—they cannot be touched or weighed.
However, they are commonplace, direct experiences, and they are as real as anything can be.
All these together make up our second world, the spiritual one."
--Rabbi Adin Steinsaltz
From Simple Words by Rabbi Adin Steinsaltz