Finally: The Summa Zoologica

Vivian Yongewa
4 min readSep 19, 2022

Or At Least the Second Volume

Photo by Lachlan Gowen on Unsplash

Let’s start with if you should read this beast of a book.


Or, actually, you should, but only if you are interested in the state of scientific knowledge and thought in the mid-1200’s, when Albertus Magnus published his work.

Otherwise, it is a real slog to get through. Let us summarize here:

The Summa Zoologica, Volume 2, translated from the Latin

It starts with Book 10, which is a discussion of how to learn about life. He advocates for a general knowledge to more specific knowledge approach. I think Vygotsky and his ladder of knowledge would approve.

Book 11 is about naming groups of animals and determining where each animal goes. This is not the mammals, reptiles, birds, and such that you know. Animals are broken down into how they move.

Book 12 is about the things all lifeforms share, relying heavily on humoral theory and the notion of balance.

Book 15 is about different modes of reproduction. Book 16 is all about how the sperm carries the spirit, and the mother provides ‘only’ the form. Book 17 is all about eggs and conception. (He thinks the spirit gets its passion from the body form, so he isn’t completely against bodies.)

Book 18 is about how perfect animals get variety in their offspring. Now, his notion of perfect is a little hard to follow here. He has a whole chapter on the difference between perfect and imperfect animals, and I think he means that a perfect animal is one with a soul that is separate from the other spirits and powers running the body, even though other animals can have a rudimentary type of soul. I am not sure I understood him, honestly. My eyes were glazing at the sheer amount of verbiage at this point.

Book 19 is a summary of everything that went before. Credit where credit is due; Albertus Magnus knows how to organize a textbook. He tells you what he’s going to do, does it, and then recaps what he did.

Book 20 goes straight into Medieval cosmology and its effects on animals. He goes over humors and how they form body parts, and he holds forth for a chapter or two on light being a fifth element or essence that binds everything.

Book 21 is the imperfect animal vs perfect animal chapter and how they reproduce. Just remember that humans are the most perfect animal.

Book 22 is a list of specific animal traits and a list of animals with specialized information. The longest entries are for creatures like dogs and donkeys, which we would all be very familiar with and observe a great deal.

Snakes get Book 25, and bugs get the last book.


Sometimes, the surprising part is what he got right. He understands the divided stomachs of ruminants and something about nerves. They knew octopuses were super smart. He’s not completely off base about everything.

But the need to shove the soul into everything keeps framing all his questions so that he can’t progress. I am sorry, but mixing spiritual questions of where the soul comes from into basic biology leads a person astray. It makes him start with an answer (humans are the most special creatures, nature never does anything needlessly) and work backward from that central assumption. For example, he thinks people have hands because we are the smartest creatures, so Nature gives us hands so we can prove how smart we are. It’s circular logic from a guy who is clearly very smart and wouldn’t use this thinking in other areas.

Not shockingly, he keeps reasoning that Nature is perfect (the perfect world hypothesis runs rampant through his work.) I am tempted to say that he is just substituting Nature for God, but he may be making a distinction that I miss simply because I haven’t read his other works.

The Big Lesson

What I really want to drive home is that Medieval scholars were not just parroting Aristotle or Galen. Far from it. And frankly, science is built on the work of former scientists. Albertus Magnus engages in the ideas of the ancient naturalists and reasons out, using logic, experimentation, and observation, which ancient got the closest to correct.

That’s right. Bacon wasn’t the first to rely on experiments to find things out about the world.

Albertus Magnus is also talking to people making direct observations and sometimes relying on his own experiences. He keeps referring to king bees because that is what bee farmers kept calling the queens of their hives. The only time Magnus dismisses an observation from the farmers is when they (correctly) identify the drones as male. For some reason, he thinks the drones are some Greek thing called Krkykis, which seem coded male but not, somehow. I’m not sure what his logic was there.

So, that is probably a lesson for today. Sometimes, direct observation is good. It was what lead Magnus to reject the idea of the expanding gall bladder.

Sometimes, though, observation can lead you astray. King bees, anyone? Next time someone swears they have a trained observer on their side, remember that the experts on the ground may be biased or not understanding what they are seeing.



Vivian Yongewa

Writes for content farms and fun. Has an AU historical mystery series on Kindle.