Dante's Really Bad Biology
03/29/2025
Dante's cosmology is intrinsically a stumbling block for the modern reader. Unless some truly astonishing revolution in scientific knowledge takes place, we are, and have been for centuries now, in a position to say that we know that his Ptolemaic system (with Christian modifications) of concentric spheres with earth at the center is incorrect. And so we have to suspend our disbelief. But that's not so very hard to do, because the scheme is straightforward, and, more importantly, it fits what everyone on earth can plainly see. It is not, as ignorant folk of our own time might suppose, something invented to support religious doctrines, but a product of close observation and mathematical skill. Ptolemy was a serious astronomer and mathematician and his system, according to Wikipedia, "included the only mathematically sound geocentric model of the Solar System."
In the Purgatorio, Dante has emerged from Hell into the actual physical world that we know. The mountain of Purgatory may not exist, but as an imaginative construct it is placed in the southern hemisphere of this planet, and its position worked out carefully. Dante demonstrates this in the opening of several cantos when he specifies the time of day by means of an elaborate picture of the position of the sun, moon, and planets, including references to various constellations and to Roman mythology. Personally I find most of these maddeningly complex, impossible to follow without help, and tiresome. For instance, Canto II (Longfellow's translation):
Already had the sun the horizon reached
Whose circle of meridian covers o’er
Jerusalem with its most lofty point,And night that opposite to him revolves
Was issuing forth from Ganges with the Scales
That fall from out her hand when she exceedeth;So that the white and the vermilion cheeks
Of beautiful Aurora, where I was,
By too great age were changing into orange.
You can get the idea that it's dawn there in Purgatory. But Dante is also informing us that it's sunset at Jerusalem and midnight at the Ganges, where the constellation Libra (the Scales) is visible (just rising, I think). You may not realize, as I would not have without notes, that full understanding of the image requires noting the fact that, as Peter Bondanella says in a note to his edition of the Longfellow translation:
The horizon of a location on earth may be described by a circle that is perpendicular to that point's meridian circle (the meridian circle is a circle passing through the point and the north and south poles).
And of course you need some knowledge of the constellations and their relationship to the seasons--the time is spring, and just past the equinox.
But this and all such constructs in the Purgatorio are astronomically accurate. The obvious conclusion of anyone walking around on the surface of the earth who has not been told otherwise is that the sun, moon, and stars circle the earth. It took a great deal of study and specialized equipment to prove otherwise, and the discovery leaves the accuracy of age-old observation intact as far as it goes. That people who lived before the Copernican revolution did not know that the facts behind the appearance were not as they seemed did not affect their ability to observe intently and accurately, more so than do any of us who aren't astronomers.
Dante's biology, on the other hand, is an altogether different story. In Canto 25 of the Purgatorio, Dante, who is now accompanied not only by Virgil but by another Roman poet, Statius, who was a Christian and, unlike Virgil, is in Purgatory as a pilgrim and not a visitor, asks a question which had also been bothering me: given that the souls in Purgatory do not have physical bodies, how is it that those they have just encountered, who are starving as their penance for gluttony, appear emaciated? For that matter, how does this whole mechanism of meeting and conversing with "souls" work? As part of his answer Statius begins to explain human reproduction:
The perfect blood, which never is drunk up
Into the thirsty veins, and which remaineth
Like food that from the table thou removest,Takes in the heart for all the human members
Virtue informative, as being that
Which to be changed to them goes through the veinsAgain digest, descends it where ’tis better
Silent to be than say; and then drops thence
Upon another’s blood in natural vase.There one together with the other mingles,
One to be passive meant, the other active
By reason of the perfect place it springs from;And being conjoined, begins to operate,
Coagulating first, then vivifying
What for its matter it had made consistent.
There's more. But somewhere in there I stopped reading and said something like "What the hell is he talking about?" As Longfellow's expression is often pretty convoluted, I keep Anthony Esolen's translation at hand while I'm reading. So I turned to it, and then to his note when the poetry proved little more intelligible, and was pleased find that he begins by remarking that this is "No one's favorite canto." Esolen goes on to give a very sound theological explication and justification for the treatment of the soul-body question in this canto. But it doesn't make the details of the biology any more sound. I called this "Dante's biology," but of course he didn't make it up. It goes back to Aristotle, at least.
I'm not going to reproduce the lengthy detailed explanation given by either Esolen or Bondanella. You don't care, and neither do I. A brief summary of what I've quoted is: there are different "grades" of blood in the body, and the more pure does not go out to nourish the rest of the body, but in the male is retained and becomes semen, which in the sexual act is mingled with female blood, and the combination turns into a body.
Eventually the question about the bodies of these shades is answered: "...the intellect imprints the circumambient air with its own form, a body that conforms itself to the intellect's desires and suffering." (Esolen) It's very Thomistic, but Bondanella notes that it was invented by Dante and has no support in Church teaching, but is a necessary device for the whole premise of the poem--that Dante can converse with the souls he encounters.
Well, it was a question that needed answering, however odd a detour the biology seemed. It didn't interfere with my enjoyment of the Purgatorio, which was greater than on my previous reading. I finished it a few days ago and I think it may prove to be my favorite of the three books. Unless something prevents me from reading at least two cantos per day, I should be able to carry out my plan of reading the Divine Comedy during Lent.