Jung's book "The Philosophical Tree" analyses the imagery of the "tree" in depth, which has similarities to trees from the ancient Chinese mythology "Shanhaijing". It is an important work for understanding Jung's thought, as it illustrates many important concepts in analytical psychology through 32 paintings related to trees. Jung preferred to use the "tree" theory to construct the interrelationship between the unconscious and the conscious, which became his choice of expression for his theory of the unconscious.

Jung writes that "the form of mental activity which lies beneath the archetypal imagery retains its character at all stages of development, although from an empirical point of view it may take innumerable variations. The outward form of the tree may change over the course of time, but the richness and vitality of the symbol are expressed more in the change of its meaning." Trees have long been a symbol of life and growth, and their significance has remained unchanged throughout history. From the towering redwoods to the delicate cherry blossoms, each tree has its own unique character that is preserved through its development. Although the physical appearance of a tree may alter as it grows, its symbolic value endures. The tree represents strength, resilience, and stability, as well as renewal and regeneration. It is a reminder that even in the face of adversity, life continues to thrive and flourish. The changing seasons bring new meaning to the tree's symbolism: in spring, it represents rebirth and renewal, while in autumn, it embodies letting go and shedding old habits. Whether standing alone or part of a larger forest community, the tree is a powerful symbol that transcends time and culture. Its beauty lies not only in its outward form but also in the depth of meaning it holds for those who contemplate its significance. 
If Freud, through the iceberg theory, uncovered for the world a huge iceberg hidden deep beneath the sea level, Jung preferred to use the "tree" theory to construct the interrelationship between the unconscious and the conscious. The "tree" theory became Jung's choice of expression for his theory of the unconscious. Jung writes that "the form of mental activity which lies beneath the archetypal imagery retains its character at all stages of development, although from an empirical point of view it may take innumerable variations. The outward form of the tree may change over the course of time, but the richness and vitality of the symbol are more often expressed in the alteration of its meaning."
From the many 'tree' forms painted by the visitors, Jung selects 32 of them and introduces them in simple, clear language, describing the original imagery of the 'tree' forms and the hidden meanings of each work. Some of the 'tree' forms express the collective human unconscious, while others represent the individual consciousness of the visitor, and there are a number of points of convergence between the paintings of the collective human unconscious and the written descriptions of trees in ancient Chinese mythology There are many similarities between the paintings of the collective human unconscious and the ancient Chinese mythology of the tree.