In biblical symbolism, the walnut's hard shell and nourishing kernel serve as a metaphor for the duality of human existence: the outer shell represents the physical body, while the inner nut signifies the soul or spirit. Early Christian thinkers, notably St. Augustine, drew parallels between the walnut and Christ—the shell likened to the wood of the Cross, the skin to Christ's flesh, and the kernel to His divinity (see 'Sermons on the New Testament'). The act of cracking a walnut thus becomes an allegory for breaking through worldly obstacles to access divine wisdom or grace. The walnut tree itself, with its hidden fruit, can be seen as a symbol of blessings or wisdom that require diligent seeking, resonating with Proverbs 2:4: 'If you seek her as silver and search for her as for hidden treasures.'

In Buddhist symbolism, the walnut can represent the mind's latent potential for enlightenment, concealed beneath layers of ignorance (avidya). The hard shell is analogous to the delusions and attachments that obscure one's true nature, while the kernel signifies the Buddha-nature inherent in all beings. The act of cracking the walnut parallels the practice of meditation and mindfulness, which gradually dismantle these barriers. The walnut also reflects the Middle Way: balancing effort (to crack the shell) and acceptance (of what lies within).

Culturally, walnuts have been enduring symbols of wisdom, fertility, and prosperity across many societies. In European folklore, walnuts were believed to grant prophetic dreams or protect against evil influences. In Chinese culture, walnuts are associated with longevity, health, and the nurturing of the mind. The act of cracking walnuts often symbolizes overcoming challenges and reaping rewards, while sharing walnuts can signify friendship, communal abundance, and the strengthening of social bonds.

In Hindu philosophy, the walnut's structure mirrors the concept of the atman (soul) encased within layers of maya (illusion) and prakriti (material nature). The shell signifies the physical and subtle bodies, while the kernel represents the pure self. Cracking open the walnut is analogous to spiritual practices (sadhana) that dissolve ignorance and reveal the atman. Walnuts are also associated with wisdom and intellect (buddhi), as their shape resembles the human brain, and are sometimes offered in rituals seeking mental clarity and discernment.

In Islamic dream interpretation, walnuts and other nuts are often seen as emblems of sustenance, hidden knowledge, and lawful provision (rizq). The hard shell signifies the effort and perseverance required to access what is beneficial, reflecting the Quranic principle that reward is commensurate with effort (Quran 53:39). Classical interpreters such as Ibn Sirin suggest that seeing walnuts in a dream may indicate lawful wealth acquired through persistence, or wisdom that is not immediately apparent. The act of cracking a walnut can symbolize overcoming obstacles to attain spiritual or material gain, and the kernel represents the reward of patience and diligence.

Psychologically, the walnut is a potent symbol of the mind, particularly the brain, due to its physical resemblance. Dreaming of walnuts may reflect the process of accessing deeper layers of consciousness or unlocking repressed memories and insights. The hard shell can symbolize psychological defenses or barriers, while cracking it open suggests breakthrough moments, self-discovery, or problem-solving. Consuming walnuts in a dream may represent the integration of new knowledge or experiences into one's psyche, signifying growth and mental nourishment.

Spiritually, the walnut encapsulates the journey from surface appearances to inner essence. The shell stands for the ego or superficial layers, while the kernel embodies the true self or spiritual core. Many mystical traditions use the metaphor of opening the walnut to describe spiritual awakening—transcending surface distractions to access deeper truths. The nourishing quality of the walnut further signifies spiritual sustenance gained through inner work and contemplation.