An important aspect of all education is to enhance students' abilities to reason critically and analytically. This is common ground for all subjects, including history, which is the focus of this study. Historical counterfactuals have been suggested as valuable tools for enhancing student reasoning about, and understanding of, historical explanations, although some of the researchers who have promoted their use also suggest that such use must be qualified (Chapman, 2003; Woodcock, 2011; Huijgen & Holthuis, 2014). However, while counterfactuals have been debated within historiography for a long time (Carr, 1961; Gaddis, 2002; Evans, 2014), little has been done about how counterfactuals can be practically applied in history teaching. A few studies done on the subject indicate that counterfactuals do have potential for engaging students in thinking about historical explanations (Buxton, 2010, Roberts, 2011; Carroll, 2018), but in order for counterfactuals to be a more effective tool in teaching and learning history, a more thorough idea of how counterfactuals can be considered as qualified is needed. In particular, students' use of counterfactuals needs to be investigated.

This need forms the basic research problem of the present study, which aims to investigate how history students use counterfactual statements when discussing possible explanations of a historical event. The research questions used in the study are:

1) To what extent do students use historical counterfactuals in their reasoning when tasked with discussing different explanations of a historical event?

2) How can the counterfactuals used by students be categorised as more or less qualified for advancing understandings of historical explanations?

While the study is set within the context of the Swedish educational system, the study aims at theoretical generalisation, complementing the studies done in England and the US on the use of counterfactuals in history education.  

The theoretical framework for analysing students' counterfactuals is inspired by Woodward's (2003) counterfactual theory of causal explanation. According to Woodward, causal explanations can be understood as 'exhibiting patterns of counterfactual dependence', meaning that they can, at least hypothetically, answer the question 'what if things had been different?' (p. 191). While Woodward's theory forms the epistemological basis for taking counterfactuals seriously, its application to history is built upon proponents of some variation of his theory arguing that counterfactuals are an integral part of all historical explanations (Nolan, 2011; Seppälä, 2012; Sunstein, 2016; cf. Weber, 1949).  It follows that consideration of counterfactuals form an important aspect of understanding historical explanations.

In order do distinguish counterfactuals that are valuable for enhancing understanding of explanations from counterfactuals that are not so valuable, four different criteria have been identified in the theoretical debate about historical counterfactuals:

- Minimal manipulation: does the counterfactual rest on changing a single factor, or several? (Sunstein, 2016; Maar, 2016; cf. Woodward, 2003),

- Direction: is the counterfactual forwards- or backwards-oriented in relation to the event that is to be explained? (Rosenfeld, 2016),

- Context-sensitivity: how does the counterfactual agree with otherwise known facts about the historical situation? (Evans, 2014; Maar, 2016)

- Evidence: to what extent is the counterfactual supported by the use of comparisons and/or generalisations? (Lebow, 2010; Seppälä, 2012)

The empirical material for the study is made up of written student answers to a prompt asking them to evaluate two different explanations to the Nazi seizure of power in Germany in 1933, with the different explanations placing varying importance on Hitler as an individual actor. This particular event was selected in order to give the students participating a relatively well-known event, increasing the chances of them knowing enough about the historical context to be able to reason about different explanations to it. The prompt was designed with upper secondary school students in mind. Participants were found by asking teachers through social media, and teachers who expressed interest were informed about the nature of the prompt and asked to test the prompt with their students. In total, six teachers from different schools in Sweden agreed to do this, yielding a total of 139 student answers. The material has been analysed in two steps, an initial content analysis in order to locate counterfactual statements in the texts. Then the counterfactuals were categorised using the theoretically derived criteria. These categories were modified with regard to empirical findings that did not map exactly to the theoretical criteria.

Out of the 139 students participating in the study, 113 made use of some kind of counterfactual statement in their response. The types of counterfactuals formed by the students display a wider register than the theoretical criteria. A small number of students used form counterfactuals that are ill-suited for displaying deeper understanding of historical explanations, most commonly by not adhering to the principle of minimal manipulation. Others formulated counterfactuals that are in principle useful for this purpose, but are too generic to actually work for the purpose. However, most students did formulate counterfactuals that, although limited in different ways, were specific enough to be discussed in relation to the criterion of context-sensitivity. A smaller number of students used some kind of evidence, either comparison or generalisation or both, in order to support their counterfactual reasoning. Thus the results of the study indicate 1) that counterfactual reasoning is a fruitful approach for engaging students in thinking about historical explanations, and 2) that the theoretical criteria can be used for distinguishing qualities in historical counterfactual statements. This makes up one way of assessing students' understanding of historical explanations.

Buxton, E. (2010). Fog over Channel; Continent inaccessible? Year 8 use counterfactual reasoning to explore place and social upheaval in eighteenth -century France and Britain. Teaching History 140, 4-15. Carr, E.H. (1961). What is history? New York: Random house. Carroll, J.E. 2018, Couching Counterfactuals in knowledge when explaining the Salem witch trials with Year 13. Teaching History 172, September 2018. 18-29. Chapman, A. (2003). Camels, Diamonds and Counterfactuals: a model for teaching causal reasoning. Teaching History 112, 46-53. Evans, R. J. (2014). Altered Pasts. Counterfactuals in history. London: Abacus. Gaddis, J.L. (2002). The Landscape of History. How Historians Map the Past. Oxford: Oxford University Press. Huijgen, T., & Holthuis, P. (2014). Towards bad history? A call for the use of counterfactual historical reasoning in history education. Historical Encounters: A journal of historical consciousness, historical cultures, and history education, 1(1), 103-110. http://hej.hermes-history.net/index.php/HEJ/article/view/36 Lebow, R.N. (2010). Forbidden Fruit: Counterfactuals and International Relations. Princeton: Princeton University Press. Maar, A. (2016). Applying D. K. Lewis's Counterfactual Theory of Causation to the Philosophy of Historiography. Journal of the Philosophy of History 10:3, 349-369, DOI: https://doi.org/10.1163/18722636-12341349 Nolan, D. 2011. Why historians (and everyone else) should care about counterfactuals. Philosophical Studies (2013), 163:317-335. DOI: 10.1007/s11098-011-9817-z Roberts, S.L. (2011). Using Counterfactual History to Enhance Students' Historical Understanding. The Social Studies 102, 117-123. DOI: 10.1080/00377996.2010.525547 Rosenfeld, G. D. (2016). The Ways We Wonder 'What If?' Towards a Typology of Historical Counterfactuals. Journal of the Philosophy of History, 10:3, 382-411, DOI: https://doi.org/10.1163/18722636-12341343 Seppälä, P. (2012). Counterfactuals and Causal Explanation in Historiography. University of Helsinki. Sunstein, C.R. (2016). Historical Explanations Always Involve Counterfactual History. Journal of the Philosophy of History 10:3, 433-440. DOI: https://doi.org/10.1163/18722636-12341345 Weber, M. (1949). Objective possibility and adequate causation in historical explanation. In Weber, M., On the Methodology of the Social Sciences, pp. 164-187. Glencoe (Il): The Free Press. Woodcock, J. (2011). Causal explanation, in Davies, I. (Ed.), Debates in History Teaching. Oxon: Routledge. 124-136. Woodward, J. (2003). Making Things Happen. A Theory of Causal Explanation. Oxford: Oxford University Press.