"In several works he used alchemical principles and symbols without hesitation to demonstrate theological realities. Borrowing alchemical terminology in order to explain religious and mystical frameworks, Böhme assumed that alchemical language is not only a metaphor for laboratory research. Alchemy is a metaphysical science because he understood that matter is contaminated with spirit." Calian 2010, p.184.
I can understand how writers like Böhme borrowed alchemical terminology, but I don't see how it follows that this means that alchemy was "not only a metaphor." If he's using it as a metaphor to make a theological point, isn't it important that the metaphor be a metaphor? It is not at all clear to me how this borrowing is evidence of alchemy being a "metaphysical science." Neither is it clear how this notion of "matter contaminated with spirit" makes alchemy more than a metaphor. Since there is already a theological reality to be described that doesn't necessarily require an alchemical explanation, it seems that to privilege the alchemical side of the metaphor is to fail to do justice to the theological side. Obviously alchemy has a spiritual important since it is being used to explain this theological reality, but we run into huge problems when we try to exalt it as a "metaphysical science."