He wielded his sharp mind like a scalpel and a digging tool, and was in many ways the model of Greek rationalism. Second only to Hippocrates, Galen is the most important person in the rise of Western medicine.
He owed his career and, by his own account, his life, to dreams of a god. He was born in
He wrote some of his medical books under direction from Asklepios. When he was at the height of his career, the god cautioned him not to go on an eastern campaign with Marcus Aurelius. He may have won the emperor’s indulgence because Marcus Aurelius thanked the gods for granting him “assistance in dreams” and especially for showing him “how to avoid spitting blood and fits of giddiness.” Later in Galen’s writing career, Asklepios reproached him in a dream because he had not completed a treatise on the optic nerve; he then pushed himself to finish this work.
As he recorded medical case histories, Galen paid close attention to the appearances of the god in diagnosing and prescribing for different ailments, and in facilitating direct healing. He was in no way superstitious. It would have been irrational, from his perspective, not to work with a friendly god who could fix the parts other medicine could not reach – and demonstrated this again and again.
The surviving text of Galen’s essay On Diagnosis from Dreams shows his no-nonsense approach. He explains that dreams can provide accurate diagnosis because during sleep the soul travels inside the body and checks out what is going on. He notes the need to distinguish a somatic dream of this kind – for which he uses the word enhypnion – from other types, such as those that originate in waking thoughts and actions, or the prophetic dream (oneiros). He is especially interested in dream weather, believing that an excess of moisture or dryness, of heat or cold in a dream, will indicate the action that needs to be taken to balance a patient’s “humors”, or vital energies.
He notes a cautionary example of how a dream warning was missed when a patient’s dream that one of his legs was turned to stone was interpreted symbolically instead of more literally. “This dream was interpreted by many skilled in these matters as a reference to the man’s slaves. However, contrary to all of our expectations, the dreamer became paralyzed in that leg.”
Galen prided himself on his ability to use his observation and intuition to diagnose emotional, as well as physical, problems. Called to treat a woman who was suffering from insomnia, he noticed that her pulse became wildly disturbed when the name of a handsome dancer, Pylades, was mentioned, but remained unaffected when he mentioned the name of a rival dancer. Galen diagnosed love-sickness.
And then there are the dreams where the god appears, to prescribe and to cure. Sometimes he does this by issuing prescriptions that might puzzle even the most adventurous physician. In one case reported by Galen, a “foreigner” came to the temple at Pergamon, in response to a dream, and had a visionary encounter with Askeplios in which he was directed to drink “a drug made from vipers”, and then smear the potion on his skin. This produced an ugly skin condition, which disappeared as the patient was healed. One scholar suggests that “viper” – echidne – should be read as “wild fig”, echinos, which certainly sounds less scary, but hardly less strange.  And we must never forget the vital importance of the “health-bringing snakes” in the Asklepian religion.
One of the benefits of divine dreams, according to Galen, is that patients are more willing to comply with directions from a god than from a regular doctor. “In Pergamon we see that those who are being treated by the god obey him when on many occasions he bids them not to drink at all for fifteen days, while they obey none of the physicians who give this prescription.” 
The god may also offer an Rx that addresses the whole person, rather than merely the symptom. Galen believed that this approach was at the heart of healing. In one of the most striking fragments from his works (many of which perished in a fire in the
We don’t want to miss the place of healing in Galen’s city of
Aristides tells us that “this well is the discovery of the great magician who does everything for the safety of mankind.” For many it “is like a drug.” By bathing in it, the blind recover their sight; by drinking from it many are cured of chest trouble and regain “the breath of life.” The lame get up and walk. Some who drink from the well become prophetic. “For some merely drawing up the water has been like a means of safety.” 
No surprise, then, that Galen not only reports dreams as clinical data, but includes an invocation to Askelpios when he administers medical treatment, as he did with these words for an emperor: “Be gracious, blessed Healer, you who made this remedy; be gracious and send your always gracious daughter Panacea to the Emperor, who will offer pure sacrifices for the freedom from pain which you can grant.”
1. Steven M.Oberhelman, "Galen, On Diagnosis through Dreams" in Journal of the History of Medicine and Allied Sciences 38 (January, 1983) p.38.
2. Emma J. Edelstein and Ludwig Edelstein, Asclepius: Collection and Interpretation of the Testimonies (second edition, Baltimore and London: Johns Hopkins Press, 1998).Testimony 401, p.202
3. ibid.,Testimony 413, pp. 208-9.
4. Aelius P. Aristides, Complete Works trans. Charles A. Behr (Leiden: E.J.Brill, 1981) 2 vols. 2:.237
Image: The Healing of Archinus, ex-voto tablet, c. 370 BCE in the National Archaeological Museum, Athens. The tablet commemorates an act of dream healing in the shrine of Amphiaraos in the city of Oropos,on the border of Boeotia and Attica. The deified king of Argos, Amphiaraos, was credited with powers of healing and his cult, like that of Asklepios, featured dream incubation. On the right side of the tablet, the patient is asleep or dormant on a couch. In the left foreground, Amphiaraos, like a mortal physician, is treating the patient’s right shoulder. At the same time, a sacred snake is licking or biting the same right shoulder of the sleeping patient. Behind, on a pillar, a votive stele commemorates the god’s act of healing. The figure on the right may be a third representation of the patient Archinus,giving thanks for his healing.
Text adapted from The Secret History of Dreaming by Robert Moss. Published by New World Library.