Podcast Summary

Podcast: New Books Network
Episode: Adam R. C. Humphreys and Hidemi Suganami, "Causal Inquiry in International Relations" (Oxford UP, 2024)
Host: Stephen Sikevich
Guests: Adam Humphries, Hidemi Suganami
Date: September 20, 2025

Overview: Main Theme and Purpose

This episode dives into "Causal Inquiry in International Relations," a new book by Adam R. C. Humphreys and Hidemi Suganami. The episode explores the enduring debates around causation in international relations (IR), examining philosophical, methodological, and practical approaches to explaining causes in world politics. The authors aim to interrogate and clarify the conceptual underpinnings of causal inquiry, bridging the gap between philosophical abstraction and empirical research methods, and offering meta-theoretical insights for IR scholars.

Key Discussion Points and Insights

1. Origins and Motivation for the Book

• Background: Humphries and Suganami met 20 years ago, sharing deep interests in IR theory and the philosophy of explanation (04:17).
• Collaboration: Although 30 years apart in academic age, their mutual fascination with causation, particularly the quality and logic of argument by major IR theorists (e.g., Waltz, Bull), laid the groundwork for this project (04:17–06:37).
• Process: The book took longer to write than planned, with hundreds of exchanged emails and close collaborative scrutiny of every paragraph (04:17–06:37).

2. The Book’s Aim: Bridging Philosophy & Methodology

• Philosophical Underpinnings: The book is split into "Metaphysics" (analyzing deep philosophical assumptions) and "Methodology" (practical implications), ultimately advocating for careful, logical reasoning over importing philosophical dogmas (08:06–09:14).
• Caution on Philosophy: Rather than simply adopting the views of major philosophers, the authors critically assess their relevance and limitations for IR causal inquiry.

"It's philosophical in orientation, but it's not like us. So and so is a great philosopher whose ideas we can use... It isn't a book like that."
— Hidemi Suganami (08:06)

3. Defining ‘Causal Inquiry’ in IR

• Terminology: The authors avoid ‘causality’ due to its metaphysical connotations, preferring ‘causal relations’, ‘causing’, and ‘causal inquiry’—focusing on “something bringing about something else” among events (10:53–13:17).

"We understand causation as bringing about something, bringing about something else. And ideas about bringing about are just ubiquitous..."
— Adam Humphries (13:17)

• Logic of Causal Inquiry: Inquiry does not only serve explanation, but also prediction and prescription, each linking differently to empirical evidence (10:53–13:17).

4. Anatomy of Causal Debates in IR

• Two Traditional Strands:
  • Philosophical-Metaphysical: Is causation ‘real’?
  • Technical-Methodological: How to empirically identify causal relationships?
• The Gap: The book situates itself between these extremes, focusing on how and when we can be confident in causal claims (14:32–16:09).

"We're a bit skeptical about debates about metaphysics... and the gap in the middle... is a gap about how can we be confident or when can we be confident that in our causal knowledge claims..."
— Adam Humphries (14:33)

5. Influential Philosophers: Hume, Bhaskar, van Fraassen

• David Hume:
  • Often misunderstood; not directly concerned with discovering what causes what, but how the idea of causation arises despite unobservable causal ‘necessity’ (16:30–20:50).
  • Hume is agnostic, not strictly a ‘regularity theorist’ or a ‘causal idealist’, transcending common IR dichotomies.

"[Hume] leaves that question alone... he remains agnostic about it. So... there is such a thing as agnosticism."
— Hidemi Suganami (16:30)

• Roy Bhaskar and Critical Realism:

  • Highly influential in IR, but Bhaskar’s arguments for causal realism are, in their view, flawed and overstated (22:36–28:22).
  • Value lies in his differentiation between open/closed systems and experiment’s power to rule out alternatives—providing important methodological insights.

• Causal Mechanisms: Popular but potentially misleading term in IR, often used metaphorically; true value is in asking for deeper information about how events are brought about (28:41–31:46).

6. Concrete and Abstract Causal Claims

• Distinction:
  • Concrete Statements: Refer to specific historical events (e.g., "the short circuit caused the fire")
  • Abstract Statements: Express causal propensities (e.g., “revolutions cause wars”), not statistical generalizations but conditional claims (46:44–51:44).

"Revolutions cause wars is... a relation that will play out if nothing else interferes. But that's a sort of conditional statement."
— Adam Humphries (47:46)

7. The Logic of Causal Inquiry

• Empirical Support: Empirical evidence relates to concrete events, but our interest is often in abstract claims. Establishing causal claims moves from evidence about specifics to conditional theoretical knowledge (54:57–58:54).
• Balance: Start from the concrete, move to the abstract—but don’t mistake propensities for regularities.

8. Types of Reasoning & Explanation

• Forms of Reasoning:
  • Induction: Generalization from repeated cases (not suitable for causal inference in IR)
  • Deduction: Logical derivation from theory (limited in practical research)
  • Abduction: “Inference to the best explanation”—fits causal inquiry best (64:33–69:13).

"When we try and reason that, oh, this thing led to that thing... it's abductive. It's saying, look, the best sense we can make... was that this event... contributed to it."
— Adam Humphries (65:58)

9. Implications for IR Theory and Practice

• Meta-theoretical Focus: The book is not another ‘ism’; it seeks to sharpen how causal claims are made, rather than advocate for a grand theory or paradigm (69:57–73:48).
• Concrete-First, Theory-Building Approach: Encourages skepticism toward the “culture of generalization” and the over-emphasis on paradigmatic battles, advocating instead a flexible, context-driven inquiry.

"Our intervention, if you like, is metatheoretical rather than theoretical... Don't buy into this notion that somehow you are inferior because you're not producing anything that is not generalizable."
— Hidemi Suganami (69:57)

• Value in Diverse Paradigms: Flexibility and openness to various paradigms, but never being confined by them. Each event/context deserves methodical, critical causal inquiry (76:43–77:57).

10. Bridging IR, History, and Historical Sociology

• Historians and IR: Historians’ focus on concrete events complements IR’s abstraction, but both must recognize the abstract implications of concrete explanations (58:54–61:34).
• Call for Integration: The authors see value in interdisciplinary approaches and breaking barriers between history, sociology, and IR (87:05–89:15).

Notable Quotes & Memorable Moments

• On Book Collaboration:
  "There's not a paragraph that went into print without each of us reading it and then approving it, scrutinizing it, approving of it."
  — Hidemi Suganami (06:37)

• On the Value and Limits of Philosophy in IR:
  “The book is in two parts. First part is called metaphysics, and the second part is called methodology... but it's more like from metaphysics to methodology. That is to say, leaving Metaphysics behind...”
  — Hidemi Suganami (08:06)

• On Abductive Reasoning:
  “We can be confident that one thing caused the other when this is the best account we can give of how that other thing was brought about... quite an ordinary common sense, everyday kind of reasoning.”
  — Adam Humphries (65:58)

• On Paradigm Battles:
  “What we’re trying to do is... what are the possible answers and which one can be deleted or ruled out on empirical evidence and therefore which is the one that we settle on?”
  — Hidemi Suganami (73:48)

• On the State of the Field:
  “One of the very frustrating dynamics in the discipline is... people who associate causation with a particular kind of approach and say, oh, no, no, that’s not for me... and on the other hand, people who... criticize any research that's not causal as not being worth having. And I think all those kinds of discussions... are really very, very unhelpful.”
  — Adam Humphries (82:50)

Important Timestamps and Segments

| Time | Segment/Topic | |-----------|-----------------------------------------------------------------| | 04:17 | The collaborative backstory of the book and authors’ aims | | 08:06 | On the book’s philosophical orientation | | 10:53 | Definition of causation and why ‘causality’ is eschewed | | 16:30 | Hume’s real significance and IR’s misreading | | 22:36 | Bhaskar, critical realism, and open systems | | 28:43 | Critique of causal mechanisms in IR | | 46:44 | Concrete vs. abstract causal statements explained | | 54:57 | Logic of causal inquiry: evidence and abstraction | | 64:33 | Types of causal reasoning: induction, deduction, abduction | | 69:57 | Meta-theoretical vs. theoretical contributions of the book | | 76:43 | Meta-theoretical flexibility and critique of paradigm constraint| | 87:05 | Integration of history/historical sociology and IR | | 92:15 | Current and future research projects of the authors |

Conclusion—The Authors' Final Reflections

• Suganami and Humphries hope their book encourages IR scholars to critically interrogate causal claims, escape the constraints of paradigmatic orthodoxy, and balance concrete inquiry with theoretical abstraction.
• Their message: begin with real-world puzzles, stay skeptical of grand theorizing unless warranted, and advance causal reasoning using clear logic and evidence.
• Both authors express gratitude for scholarly engagement and look forward to new conversations and further cross-disciplinary exploration.

Further Resources

• Causal Inquiry in International Relations (Oxford UP, 2024) by Adam R. C. Humphreys & Hidemi Suganami
• New Books Network: Series link