2 definitions
The Philosophical tree (n.) was the alchemists' name for the whole process now understood as psychological development, a "poetic" analogy between the natural growth of the psyche and of a plant.
The Philosophical tree (n.) is the alchemists' metallic tree, like Zarathustra's dream-tree of four metals; it symbolizes spiritual growth and the highest illumination, for spirit may lie as dead and heavy as lead.