Since the 1990s, inclusion has become one of the priorities of worldwide education. Nations face the challenge of promoting a paradigmatic change in education and are committed to ordering, regulating, and providing educational quality and equity conditions regardless of differences and particular challenges (e.g., UNESCO, 1994; UN, 2006). 

In general, knowledge about inclusion is produced from sociological perspectives. Although these perspectives have differentiated emphasis on the social or the individual, they are rooted in modern ontological principles and are similar in their ethical and theoretical effects. Disability is recognized as both: a consequence of individual pathologies and a socio-political, cultural, and relational phenomenon. Specifically, those empirical works that emphasize social conditions and relationships as principal agents in producing disability belong to the theoretical matrix called the social model of disability (Goodley, 2017; Runswick-Cole et al., 2018). 

Unfortunately, this type of knowledge is a primary source to public policies and educational strategies around disability, even though it has not yet fulfilled commitments towards inclusion and has disseminated a limited understanding of disability: bodies and subjectivities are still segregated in binary axes and placed in an interplay of permanent self-responsibility (Goodley, 2017; Oliver, 2013). In other words, the disabled would be able to transcend the determination of normative environments they belong to if and only if they effectively display their exclusive agency (Goodley, 2017; Shildrick, 2004).

Considering some gaps that still exist, non-governmental organizations worldwide have promoted the renewal of onto-epistemological, theoretical, and ethical discussions regarding the paradigms of inclusion, justice, and equity in the contemporary neoliberal contexts (Ainscow, 2016; Watson et al., 2012).

However, given the social model's hegemony as a theoretical framework, any other proposal to approach disability - and inclusion- might be justified using empirical evidence produced from the social model itself. Then, we think that analyzing such evidence through an ontological lens could be a way to enlighten some of its theoretical and ethical challenges. 

In this sense, phenomenological research that explores how the disabled -and other related educational actors- experience inclusion processes (Messiou, 2017, 2019) constitutes a fertile field of evidence under the social model's principles. In this type of research, discourses that embody individuals' perspectives, experiences, and affections will be called voice.

This critical literature review aims to question: What have been the voice's empirical trajectories from the social model of disability when voice is positioned as a unit of analysis of inclusion practices? We discuss some theoretical and ethical challenges that the empiric use of voice from the social model of disability poses to the knowledge and development of public policies on inclusive education. As an alternative, we suggested that new materialisms allow us to interrogate the ideas about the human and the difference underneath the social model of disability, given its modern ontological roots. In this direction, we redefined voice to recognize every minuscule difference expressed by each living materiality. Then, we reflected on the possibilities of a non-deterministic understanding of the difference and the human that encourages the becoming of new discourses, practices, and public policies for inclusion in education. 

Our corpus of review comprises 31 empirical studies located through Scopus and Web of Science (WoS- Main Collection) databases. All papers focus on "voice" - such as it is defined by the social model of disability- as the unit of analysis for inclusive practices in different educational scenarios. To search them, keywords sequence was: ("voice*" OR "experienc*" OR "narrativ*" OR "biograph*" OR "discourse" OR "subjectivit*" OR "body" OR "bodi*" OR "corporalit*" OR "student*" OR "youth*" OR "child*" OR "adolescent*" OR "parent*" OR "famil*" OR "teacher*" OR "learner") AND ("disabled" OR "disabilit*") AND ("social model of disability") AND ("Education*" OR "education*" OR "educativ*"). "Inclusion" was not explicitly used as a critical term due to - on the one hand - the diversity and breadth of meanings reported in previous studies (Duk & Murillo, 2016; Hodkinson, 2016; Manghi et al., 2020; Slee, 2014). On the other hand, we were interested that this review set an ontological critique. Thus, required articles were those where the analytical unit was specifically "voice" (or voices) of inclusion practices' actors. Search terms are then synonymous with "voice" or with those human groups whose "voice" might be of interest. Selection criteria: We considered only published papers until November 2018, where defined key terms appeared in their titles or abstracts. Besides, subject areas were restricted. In WoS were excluded: "Rehabilitation", "Language & Linguistics", "Literature Romance", "Information Science", "Library Science", "Nursing", "Orthopedics", "Public Environmental Occupational Health", "Health Care Sciences Services". In Scopus: "Medicine", "Nursing", "Biochemistry", "Genetics and" Molecular Biology "," Economics, Econometrics and Finance "," Agricultural Sciences "; "Business", "Management and Accounting", "Computer Science", "Engineering", "Environmental Science". Exclusion criteria: After applying selection criteria, the number of papers to review amounted to 79; 15 were indexed in both databases. Then, we reviewed abstracts and methodological sections of 64 articles, and 33 were excluded because they met at least one of the following criteria: 1. To be a literature review related to disability or inclusion; 2. To describe the text of one or more inclusion policies; 3. To describe institutional programs to support disability only locally relevant or with economic emphasis; 4. Do not show results produced through educational settings; and, 5. Do not refer to findings with direct consequences for inclusion in education.

We found that "voice" is systematically synonym with discourse, and it describes three empirical routes: "voice" that points out social barriers, "voice" that expresses attitudes and beliefs, and "voice" that copes with stigma. "Voice" as discourse is an analytical heuristic through which the phenomenological experience can be accessed. Although "voices-discourses" materialize bodies and subjectivities, how can we ensure that they effectively reveal them? Couldn't this same "voice" be considered also materiality with its unpredictable effects? Does only "voice-discourse" have the power to symbolize and predict living phenomena? Or, on the contrary, could we affirm that the "voice-discourse" annihilates the alive existences, for example, when it partially captures human experiences, replaces them, and artificially disconnects them? "Voice" as discourse blocks the possibility of questioning the essentialist understanding of "the human" promoted by the social model (Infante, 2018; Hickey-Moody & Crowley, 2010). Also, expressions of difference cannot be defined as agential materialities, in movement, and entanglements with others -simultaneously human and non-human, structural and subjective (Naraian, 2020)-. New materialisms could be that onto-epistemological alternative to rewrite "the difference" and "the human". From here, "voice" can be defined as an expression of living existence; a difference is a "voice". "The differences" are "voices" who speak about the multiple possibilities of "the human". We can name "voice" any minuscule difference capable of producing some effect in assemblages with other forces, with "other differences", with "other voices" (Coole & Frost, 2010; St. Pierre, 2013). It is then set as possibilities of "the human" - and not as aberrations - those multiple expressions of difference that, since they are not productive for neoliberalism, put in check inclusion projects and practices.

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