This document discusses using agent-based modeling and simulation as a form of "practical necromancy" to predict and understand the past. It begins by outlining the historical practice of necromancy and divination. It then argues that modern simulations, like agent-based models, can serve similar purposes by creating "zombies" or simulated agents following simple rules based on our understanding of past systems and behaviors. Through emergent patterns from simulating interactions between these agents, we can test and explore hypotheses about how the past may have functioned, even if we cannot prove what exactly happened. Several examples are provided of past agent-based models the author has created related to information diffusion in the Roman world. The document argues

1. Practical Necromancy!
Or
How to raise the dead to predict
the past
Shawn Graham
Carleton
University
Some rights reserved by Pedro Vezini @electricarchaeo

2. The Plan
 The deep history of
divination
 Necromancy & Death
 Simulation as modern
divination
 Nuclear War & Death
 Use our powers for
Some rights reserved by pasukaru76
good instead of evil
 Practical Necromancy &
Agent based models

3. The Restless Dead
 Zombies  Bela Lugosi – White Zombie
 Frankenstein’s Monster
When you raise the dead, there’s usually trouble.
Still from ‘I walked with a Brendon Thorne, Getty
zombie!’ 1943

4. Sometimes, zombies can be more
human than the humans.
 Fido, 2006

5.  eHow, the font of all
knowledge

6. Necromancy & Divination:
responses to the original
‘problem space’:
 How do you keep the
world from ending?
2012 Movie – there goes
New York!

7. How do we keep the world from
ending?
 Shamanism
 Involves entering an altered state,
induced through physical exertion or
drugs
 Allows the breeching of the barrier
between the everday & spiritual
worlds
 Knowledge of the other world and
being the intermediary between the
two

8. Knossos

9. Games & Simulations as
Purification
 Etruscan Games
 Roman Spectacles of Death
Grotta della Scimia Corneto, about
500 B.C

10. Magicians & Priests
 The priest is passive
in letting
signs, portents to
signify what is to
come (augury)
 But the magician is
active in dragging the
spirits forward to tell
the future
(necromancy)
(a bit like Humanities versus
Digital
Humanities, perhaps)

11. Oracles & Riddles

12. Games of Divination
 I Ching – Book of Changes
 http://www.ichingonline.net/index.php

13.  Riddles, Oracles:
 They describe a world
 They are something to be solved
 They present challenge & difficulty
 They join representation with puzzle
 Games, Riddles, Oracles: represent the
world, control the world, explore the world

14. Enough of riddles. Let’s get a
straight answer.
 Witch of Endor

15. Odysseus in the Underworld
 Book XI – Nekuia
 ("rite by which ghosts were called up and questioned about the future," i.e., necromancy.)
 Circe: You need to talk to Tiresias
 Odysseus: He’s dead.
 Circe: Yes, you need to go to the underworld.
 Odysseus: d’oh.
 Makes a sacrifice of meat, milk, honey, wine, and water; gives blood to the
shade of Tiresias
 Also gives blood to shade of his mother, Anticlea.
 And Agamemnon, and Minos, and Orion, and Tityos…. It’s busy, in the
underworld.

16. Necromancy
 Is about trying to control the
future
 This is a deep element to human
modes of being
 Unlike divination, the element of
compulsion of other spirits and gods
marks it out as something unholy
 Unholy in its means, unholy in its Prof. Hix, of Unseen
University prefers the
aims and objects term, ‘Post Mortem
Communnications’

17. Simulation is also
regarded, especially by those in
the humanities, as similarly evil
 Marney & Tarbert, 2000. ‘Why Do
Simulation? Towards a Working
Epistemology for Practitioners of the Dark
Arts' in Volume 3(4)
http://jasss.soc.surrey.ac.uk/3/4/4.html
(especially section 5).

18. Necromancy = Simulation
 Scry the future  Predict the future
 Non-human actors  Non-human actors
 Messy / Hidden  Messy / Hidden
 Left to professionals  Left to professionals
 An act of compulsion  Forcing what we know
through proper into computer
conduct of processes, algortihmns
chants, rituals, accoutr , equations
ements

19. Modern
necromancy
 Simulations of death

20. And now, a brief detour into
Science Fiction
 Isaac Asimov, Foundation
 Hari Seldon & Psychohistory

21. Practical Necromancy is not
cliodynamics
 Cliodynamics.info
 Top-down vs bottom-up
 Not about simulation, but
about aggregate patterns
Even if these patterns exist,
doesn’t explain ‘why’

22. Simulation of individual
interactions might, though.
 Garbage
in, garbage out
or the problem
of circularity

23. I object:
 In the case of humans,
 We don’t know all the variables
 We don’t know how free will works
 We don’t know how an individual will react
 We don’t understand how individuals and society
influence each other
 Prediction then becomes limited to very stringent
conditions
 (ex: pedestrian flow)

24. …it’s at this point in the talk
that heart palpitations normally
occur.
 This limitation is actually a strength, and is what
makes this ‘practical necromancy’
http://stackoverflow.com/questions/234075/what-is-your-
best-programmer-joke

25. Instead, create some zombies
 And see how they
interact!

26.  Simulate how you believe some aspect of the past
worked, at the level of individuals.
 Not the past but rather, a way of testing the
consequences of your story about the past
 Practical Necromancy is probabilistic historiography

27. Wait, how does that work
again?
 And thus can sweep the
 We create simulacra, entire behavior
zombies, empty husks space, the entire realm
representing past actors of possible outcomes
given this understanding
 We give them rules to be
interpreted given local  ...and map what did
conditions occur (as best as we
understand it) against
the predictions of the
 We watch what emerges model.

28. Next part: the practical &
grounded reasons for doing all
this.
• What they are
 Agent Based Models: • How they work
the basics • Usefulness for
 My own research history/archaeology
• Making our
assumptions about
how the past works
*explicit*

29. Complex = Complicated

30. Complexity & the problem of
levels

31. And what do we model?

32. Agent models: your own
personal Groundhog Day

33. Characteristics of an ‘agent-
based’ model

34. The ‘environment’

35. A Simple Model to Get Us
Started
 Have you heard the
news?
(see Journal of Mediterranean Archaeology 19.1 for details)

36. The Antonine Itineraries
as Network
A limite id est a vallo Praetorio
usque mpm clvi
A Bremenio
Vindomora viiii
Vinovia xviiii
Cataractoni xxii
Isurium xxiiii
Eburacum, leg. vi victrix, xvii
Derventione vii
Delgovicia xiii
Praetorio xxv

37. Reanimate: just add agents!

38. The model code:
to go
ask romans
[
pass-the-word ; if somebody here hasn’t heard the idea, tell them!
move-forward ; then follow the route of the itinerary to somewhere else
]
update-plots ; plot the percentage who have now heard the idea
if everyone-heard-it = 100%
[stop] ; if everyone has heard it, stop the simulation
set ticks ticks + 1 ; update the clock.
end

39. An Agent Based Exploration
of the Antonine
Itineraries
 http://www.graeworks.net/abm/itineraries.html

40. Interpretation
Internal Dynamicsof Provincial Information Diffusion
1
" "r pr s nts the initia numbe of time s ps to ge the
t
tion
tiona of Time S ps
me s ge to 1 % of the popula
te
te
l
r
0
P opor
l
r
s a
Iberia
1 e e e
Britain
Italy
0.1 Three Gauls
1 21 41 61 81 101 121
%Who Have Heard the Message

41. So what did my zombies demonstrate?
‘prove’ is too strong a word
The patterns of interaction,
rather than the interactions
themselves , are necessary parts of
any explanation .
Network topologies matter.
(one of Meeks’ pillars of DH is network
analysis: but SNA is static. We need to reanimate them too!)

42. PatronWorld
A Rather More Complex Model
Where patterns of
interactions again are
the key

43. Why doesn't it all
collapse?

44. Begin with something
fundamental
 Salutatio : the morning
greeting of a patron by
his clients
 And then to process to
the forum, being
seen, and seeing in
turn, who is following
whom

45. Networks derived from central
Italian brick stamp data

46.  http://www.graeworks.net/abm/PatronWorld.html

47. When Digital Romans Go Bad

48. When Digital Romans Go Bad
Oppression
Deaths
Model runs where violence emerged

49. Take Aways
 Network topology matters
 Model at the lowest practical level
 Identify one crucial aspect and
model that
 Your model encodes your beliefs
about the world: the process is the
rhetoric

50. So where I am now:
Economic Zombies
who
Generate
Networks

51. Practical Necromancy, eh?
 Divination & simulation have deep roots
 Computation actually lets us get rather good at
it, in some domains
 Even in complex systems – especially human ones –
simulation can be useful
 Create zombies, give them simple rules based on our own
mental models about the past
 Thus we simulate not the past, but a historiography
 Rigorous, explicit, open to critique and extension
 Look me up on Figshare.com

52. Final Word to Phil Connors:
I am a God.