Merriam Webster tells us that the word, empyrealcan be traced back to the Greek word for "fiery," empyros, which was formed from the prefix em- ("in," "within," or "inside") and -pyros, from pyr, the Greek word for "fire." When empyreal entered the English language—via the Late Latin empyreus or empyrius—in the 15th century, it specifically referred to things related to the empyrean, the highest heaven or outermost heavenly sphere of ancient and medieval cosmology, which was often thought to contain or be composed of the element of fire.

"But Gaius," cried Merlin, with a grin and flash of impatience. "Clearly, I can manipulate fire to take the form of shapes; I can even make them move as if they were alive. How can Plato's theory that fire rises in straight line towards the upper regions of heaven be true, when I can so easily control it?"

"Because sorcery changes and manipulates the natural order, Merlin. We are not discussing how you can distort the natural laws with sorcery. We are exploring a framework in which we can begin to understand the natural order of the world. Let's drop Plato for the moment. It is always Aristotle's view of the elements and the aether, that seems to best reflect my own observations."

"But if I already know how to control fire, how does a 'framework' help me? Plato, Aristotle…. how does this help me understand my magic?"

The old physician sighed. Sometimes Merlin's impatience to know and understand his power was greater than his desire to understand the framework of its rules. His knowledge was based more on his personal experience than actual scientific thought. Some days it was hard to refute the boy. Perhaps, he had taught him too well, to contest every statement. Gaius smiled to himself, before he went on.

"The four elements are constantly changing, but are held in balance on this plane, Merlin. The aether is unchanging, constantly in an eternal circular motion. It is this unchanging layer above us that constitutes the empyrean, the highest heaven of our cosmology. The sorcerer must understand that he or she can manipulate the elements, but the power to do so, can never affect the unchanging aether."

"Perhaps the aether is the source of all magic," said Merlin, intrigued by his own idea.

"I believe it more likely that magic arises from the interaction of the mortal elements of fire, water, air and earth. The aether is unchanging."

"So the limits of my power might be defined by which of the theories holds true," mused Merlin, with a waggish look in his eye. "If Plato is right and the empyrean is made of fire, which I can easily control, Then I should be able to draw on it for unlimited power. But if my power arises from the mortal plane, then…"

"That wasn't the point I was trying to make!"

"Now, how can I design an experiment… purely theoretical, of course," said Merlin, his voice trailing off, as the ironic twinkle in his eye grew brighter.

"Merlin," came the growling warning from the old physician.

"Yes, I know! Dangerous, " laughed Merlin. "Why do you raise these questions, Gaius, if you don't want me to go there?" His tone was all aggrieved innocence.

"Because I am committed to your education, Merlin."

"Then, it's a good thing I'm committed to yours, as well."

Gaius did not reply to this last barb, but his eyebrow flared and Merlin laughed outright. The older man offered him a cup of steaming tea, and Merlin accepted it with a deepening happiness in his eyes. It was wonderful to be able to share this forbidden side of his life, with someone else. While he considered some of his lessons tedious and was not sure how they applied to his actual use of magic, the sense of acceptance he derived from his time with Gaius, was more precious to him than he cared to admit.

He wondered sometimes what it was like for Gaius, who for years had been a sorcerer sworn to never use his powers, dwelling in the heart of the Purge that had raged through Camelot. He had stayed alive by never exposing this side of himself, It must be a comfort to him as well, to find a comrade who shared his burden. Both of them had found a companion, who had to keep a secret hidden. Gaius understood, as few people could, the price paid for the delicate balance of life in Camelot.

Merlin could not yet know that Gaius regarded him as the greatest, unexpected treasure of his life.

For now it was enough to sip a cup of tea together in the dark of the night, after metaphysical and arcane discussions. The firelight was kind to the shadows and magic whispered, until the ordinary moment became eternal. It glowed precious as an ember, in Merlin's heart.