Spirit as the fifth element represents more than what is found in Pagan beliefs. I have compiled a comprehensive view from bits and pieces found on the net in an effort to bring more clarity of meaning.

Spirit represents the prime element present in all things, providing space, connection and balance for all elements to exist.  It is essential to our sense of connectedness with spirit and well-being.  Spirit represents the sense of joy and union, transcendence, transformation, change, everywhere and nowhere, within and without, immanence.  It represents the human spirit and energy of God and  the Goddess.

Akasha is a kind of super-element: the binding force between the other elements (like gluons from particle theory), or demi-goddess or, for that sake: if you want to look at it from a scientific point of view, a kind of black hole that emanates and absorbs energy/matter. Akasha is the fifth element, the binding part that runs through all matter, and it is also the collective unconscious of life-forms. The Elements emerge from Akasha, the immutable, changeless source of all energy. This is the realm of potentiality: of promise, of paths not yet taken, of unformed galaxies, of outer space.

Akasha is also present within our bodies. Some say that the spark of life, that unknowable force that is called the "soul," is a bit of Akashic energy housed in the physical body.

Akasha is sometimes thought to be symbolically present on the Earth. More often it's seen as the Mother (Creatrix) of the elements. It's little used in natural magic, but something of its nature should be understood.

Primarily, Akasha is unbeingness. Its energy, which extends everywhere throughout the universe, has not yet achieved form and substance. It's the primal source of energy that creates and fuels the elements.

Because of this, it contains complete, balanced energy: Earth and Air and Fire and Water

Spirit, or Ether or Akasha:  Akasha is the Sanskrit word for Ether/Aether, which represents the universal inner space, the material that fills the region of the universe above the terrestrial sphere. Akasha is rooted in Hindu beliefs and is actually considered the first element by the Hindu religion. The word Akasha is actually a Sanskit word "meaning aether in both its elemental and metaphysical senses" (according to Wikipedia). Akasha is also taken to mean sky, by way of Hindu and Gujarati Indian languages. This is why Wiccans also associate Akasha with outer space or "the void".

Native Americans call this fundamental, life-sustaining energy Grandfather, or Arch of Heaven. In Hindu writing, atman is the spiritual essence of creation. Polynesians and the Jains have a similar idea but use the terms mana or jiva respectively, meaning that which animates all life, or the life principle.

In his book Modern Magick, Donald Michael Kraig explains that spirit “is the source of the other four elements. Spirit is the source of all that exists and is the divine light from beyond Keter [the first sephirah of the Tree of Life].”

Because spirit creates everything, abides in everything, and enlivens everything, it is always present. When a witch calls upon a divine being to bless a spell or ritual, she connects with spirit and invites it to participate in her magick. By honoring spirit, she elevates her workings from the physical realm to the divine one. – Skye Alexander

Akasha, the fifth element, is something that we all seek our entire lives, in one way or another. Even if you don't realize it, you are a part of Akasha and Akasha is a part of you, infinitely.