Religion-based social conflicts have recently become a serious global community challenge for the creation of harmony in relations between diverse groups. Since the events of 9/11, the problems of religion-based social relations have been worsened by the development of religious fundamentalism and extremism, as the roots of religion-based violence and terrorism (Vergani et al. 2020; Wibisono et al. 2019). Some researchers use the term religious fundamentalism to describe a strict interpretation of religious beliefs (Altemeyer and Hunsberger 1992; Liht et al. 2011; Williamson 2010). Religious-based radicalism or extremism is connected to a certain political agenda (Kruglanski et al. 2018; Simon et al. 2013; Webber et al. 2018) as an alternative to the existing system (Wibisono et al. 2019).

Ten years after 9/11, several major countries implemented several policies related to education to reduce prejudice. This started from the US in 2011 with the strategic policy of “Empowering Local Partners to Prevent Violent Extremism in the United States” (The White House 2011). The UK, in the same year, released the INSTED (In-Service Training and Educational Development) project for teachers on Sensitive and Controversial Issues (Jerome and Elwick 2020). Canada in 2013 issued a policy of “Building Resilience against Terrorism” which focuses on four aspects that are prevent, detect, deny and respond (Public Safety Canada 2013). In fact, UNESCO in 2016 and 2017 issued two policies for the prevention of radicalism in education in 2016 and 2017. The two policies were “A Teacher’s Guide on the Prevention of Violent Extremism” (UNESCO 2016) and “Preventing Violent Extremism through Education: A Guide for Policy Makers”(UNESCO 2017).

Religion-based conflict is inseparable from the concept of prejudice since social scientists assert that prejudice is the root of intergroup conflict (Allport 1954; Duckitt 2003). Reducing prejudice has an important role in creating harmony in religious diversity. Prejudice and education are inextricably linked because they both deal with the most basic component of human behavior: learning to coexist (Hughes 2017). Education is viewed as critical in decreasing prejudice, developing mutual understanding, and strengthening social cohesiveness (Banks and Banks 2016; Gill 2016; Mayhew and Rockenbach 2021; Raihani 2018; Rockenbach et al. 2015; Ubani et al. 2020; Malović and Vujica 2021).

Education is viewed as a strategic effort in a plural society to educate individuals with the knowledge, attitudes, and abilities necessary to live harmoniously in social diversity (Gill 2016; Mayhew et al. 2016; Mayhew and Rockenbach 2021; Raihani 2018; Rockenbach et al. 2015). The contact hypothesis theory states that contact between different groups can reduce prejudice when optimal conditions exist, such as equal status, group collaboration, common aims, as well as social and institutional support (Allport 1954; Pettigrew and Tropp 2008). As a result, intergroup contact is regarded as one of the most effective means of reducing prejudice (Boin et al. 2021). Contact between groups to minimize religious prejudice has been widely employed in a variety of social contexts, including education and teaching in schools and universities with the use of terminology, including ‘interfaith learning’ (Goldberg 2020; Mayhew and Rockenbach 2021), ‘inter-religious education’ or ‘interfaith education’ (e.g., Engebretson et al. 2010; Wielzen and Avest 2017), and ‘inter-faith dialogue’ or ‘inter-religious dialogue’ (Ariarajah 2019; Rydz and Wieradzka-Pilarczyk 2017). The concept behind interfaith learning is that strong interfaith interactions underlie the acquisition of knowledge, attitudes, beliefs, and behaviors for positive relationships among people of different religions or worldviews (Mayhew and Rockenbach 2021; Rockenbach et al. 2020; Wielzen and Avest 2017).

In conclusion, formal education has an essential role in providing the students with the information, attitudes, and abilities required to live harmoniously in pluralistic society, eliminating religious prejudice. Based on previous studies, various intervention programs have been carried out in educational settings to reduce religious prejudice.

Ontology deals with what exists or the nature of reality (Creswell and Creswell 2014; Neuman 2014). Ontologically, the nature of interreligious or interfaith reality in the context of education is a diverse reality. Various terminology or concepts are used for interfaith reality, such as learning, education, and dialogue. The difference in the choice of concept or terminology really depends on which side the researcher approaches the reality of the interreligious/interfaith contact.

In explaining the relationship between the intervention programs and prejudice reduction, the issue related to the ontological category that needs to be considered is the category of “relationship” between the two concepts. The “relationship” category asks whether one concept is related to another; then, how the relationship is between these concepts (Neuman 2014). For this reason, further researchers need to consider what concepts or variables explain the relationship between intergroup contact-based intervention programs and prejudice reduction. The relationship can be direct or indirect. If it is indirect, then there are other variables that act as mediators or moderators. The mechanism of the relationship between the concepts can be as causality and/or association, which can be shown in conceptual models as representational illustrations and heuristic tools that visually describe concepts and theories (Elangovan and Rajendran 2015).

Based on previous findings, one of the studies mapping the relationship between intergroup contact interventions with the formation or reduction in prejudice through mediator and moderator variables was conducted by Boin et al. (2021). The variables that can be used to explain the connection between intergroup contact and prejudice reduction are mediator variables. These mediator variables include empathy, perspective taking, trust, intergroup anxiety, intergroup threat, outgroup morality, the inclusion of the other in the self, self-disclosure, dehumanization, contact experience, outgroup heterogeneity, stereotypes/meta-stereotypes, intergroup reappraisal, and deprovincialization. Furthermore, moderator variables can be grouped into personal and contextual variables. The moderator-personal variables include RWA (right wing authoritarianism), SDO (social dominance orientation), NFC (need for closure), conservatism, big five personality traits (especially agreeableness and extraversion traits), and ingroup identification. While the contextual variables are majority–minority status groups (Boin et al. 2021).

Social relations in religious diversity are complex social realities that require an interdisciplinary approach. For example, social psychology, as part of behavioral science, connects social structures at all levels to individual identities and psychological constructs such as beliefs, values, attitudes, and behavior by combining other scientific disciplines such as sociology, anthropology, political science, history, theology, and philosophy (Herriot 2008; Williamson 2010).

2.2. Epistemological Implications

Epistemology is concerned with how we know reality or what makes true statements about reality based on ontological assumptions accurate. What has to be carried out to produce knowledge, and how scientific knowledge appears after it is generated, are both covered by epistemology (Neuman 2014). Based on the ontological principle, a researcher needs to have a clear view of reality to be able to make the right methodological choices (Lohse 2017). The selection of research methods cannot be separated from the research paradigm that comes from the epistemology and ontology adopted by the researcher (Creswell and Creswell 2014). There were two research methods used, namely quantitative and qualitative. However, in line with the chosen ontology, epistemology, and paradigm, researchers can consider choosing another method videlicet mixed-methods, which is a combination or integration of quantitative and qualitative research and data in research (Creswell and Creswell 2014), using a pragmatism paradigm (Lohse 2017; Maarouf 2019). In line with the ontological assumption of the complexity of interfaith relation problems in learning, mixed-methods is a methodological choice that can be considered for providing a broad and in-depth understanding of the complexity of the social reality being studied (Creswell and Creswell 2014).

2.3. Axiological Implications

Axiology in research refers to what the researcher considers to be worthwhile and ethical, which is enshrined in the research paradigm and guides the researcher’s decision-making (Killam 2013). Researchers in the selection of intervention programs need to consider the theoretical and practical benefits for the development of theory and science, as well as in overcoming socio-empirical problems such as prejudice, intolerance, and conflict stemming from religious diversity. For example, the intervention program ‘Camino Peace Pilgrimage’ was quite an expensive program for student participants and was exclusive, since it prevented many students from being involved in it (Allen 2016). For this reason, researchers or educational institutions need to consider the broader implication of implementing an intervention program design. For example, involving all students by making the program mandatory as part of the curriculum or course. One of the methodological issues that need attention in any experimental research to determine the effectiveness of an intervention program, including an intervention program for prejudice reduction, is selection bias. Selection bias is related to how participants (students) are enrolled in intervention programs: randomly or not. Another method to consider using when evaluating the effectiveness of an intervention program to reduce prejudice in educational settings is randomized field experiments. By this experimental method, two or more groups are randomly allocated to different intervention programs and one placebo program. This experimental method allows quantifying the causal effect of intervention programs on the outcome of interest with a high level of external validity (Neuman 2014).