The consensus of opinion interpreted the Redeemer equally as a fish and a serpent; he is a fish because he rose from the unknown depths, and a serpent because he came mysteriously out of the darkness.
Fishes and snakes are favourite symbols for describing psychic happenings or experiences that suddenly dart out of the unconscious and have a frightening or redeeming
That is why they are so often expressed by the motif of helpful animals.
The comparison of Christ with the serpent is more authentic than that with the fish, but, for all that, it was not so popular in primitive Christianity.
The Gnostics favoured it because it was an old-established symbol for the “good” genius loci, the Agathodaimon, and also for their beloved Nous.
Both symbols are of inestimable value when it comes to the natural, instinctive interpretation of the Christ-figure.
Theriomorphic symbols are very common in dreams and other manifestations of the unconscious.
They express the psychic level of the content in question; that is to say, such contents are at a stage of unconsciousness that is as far from human consciousness as the
psyche of an animal.
Warm-blooded or cold-blooded vertebrates of all kinds, or even invertebrates, thus indicate the degree of unconsciousness.
It is important for psychopathologists to know this, because these contents can produce, at all levels, symptoms that are localized to the corresponding organic or physiological functions.
For instance, the symptoms may be distinctly correlated with the cerebrospinal and the sympathetic nervous system.
The Sethians may have guessed something of this sort, for Hippolytus mentions, in connection with the serpent, that they compared the “Father” with the cerebrum and the
“Son” with the cerebellum and spinal cord.
The snake does in fact symbolize “cold-blooded” inhuman contents and tendencies of an abstractly intellectual as well as a concretely animal nature: in a word, the extra-human quality in man. ~Carl Jung; Aion; Page 186; Para 292.