The Celts followed a Tripartite Cosmology, which basically means we have a "here", "there", and a place between the two. To give you a simple and easy to follow example, imagine two rooms separated by a short passage. When moving between the rooms, you are either in one room (here), the other room (there), or between the two rooms in the passage. This passage is then what we call a liminal point between the two, and between or betwixt place. In many regards, when we create Sacred Space or Open Circle, we are in this betwixt place as we are no longer entirely in this world, and we are not yet in the OtherWorld. The Sacred Space creates that position between the two, the passageway as it were.

This Tripartite Cosmology of the Celts is further described as having three Realms, those being Land, Sea and Sky. In reference to Sky, we are speaking of the OverWorld, the sky above our heads. Land is that place beneath the surface, the UnderWorld where the Fae are found, not the land which you stand on, but deeper, beneath the surface, beneath the skin of everything whether it be a leaf or the surface of the earth, can be found as the UnderWorld. Between these two Realms we find Sea, that which connects both as rain falls from the Sky, and bodies of water flow into and out of the Land, constantly cycling as water evaporates and then falls. This aspect being apparent in the physical sense rather than the mystical as we find the Sun in the Sky, relating to Fire, which evaporates the Water on the Earth, and the process continues.

It is no wonder that because of this triune significance in the Celt's Cosmos, the number three was also reflected throughout their society. We find it in the Triads of poetry and lore, in the three classes of Druid, Vate and Bard as well in society as the warrior, the skilled and the farmer. In the poem by Amergin,The Cauldron of Poesy, we find he speaks of three energy centres in the body. A person is made of body, spirit and soul, or in relation to the person being the Cauldron, a universe or cosmos by itself, the microcosm, with three legs supporting the cauldron, those three legs being Land, Sea and Sky or Earth, Water and Fire. This use of what we generally tend to consider "the elements" should not be confused with the Neo-Pagan significance of such.

I feel my way into the rock.
I finger the dark holes of its brain.
My hands encounter the dark.
My eyes see with the sight of the rock.
I breathe out with the breath of the rock.
My fingers the wind touches, and my feet the sea washes.
My thought lies in the head of the rock—
Tintagel, gripping the White Brow.
My sweat runs in streams down the face of rock.
I mingle with the sea-salt and sea-mist.
I blow out on the wind's back.
The sky swallows my heart.
I beat with the tick of the beating world.
I beat.
The wind shakes my hair.
The sand forms itself to a pattern:
An Iron Crown, spiked and spurred.
My fingers forget they are fingers.
My body forgets all it has remembered.
I learn the secret of the birth of rock.
A seabird without wings I am swept
Into the sky—through the sky.
Air rocks my wings.
In the cave my fingers and feet
Release rock. Strands of hair
Twist in water and in air.
-Taliesin