The book Opportunities and Deprivation in the Urban South by Eduardo Cesar Leão Marques explores and analyzes a dimension which is traditionally considered secondary (and frequently ignored) in poverty studies: the relationship between sociability configurations and the (re)production of diverse conditions of poverty.

Based on a robust and rigorous empirical research with 209 individuals living in poverty situations and 30 middle-class individuals from the Metropolitan Region of São Paulo, the book is organized into seven chapters structured in the following way. The first chapter revisits a generous amount of literature devoted to the topics of poverty, segregation and social networks and seeks to build an analytical perspective that aims to show the central argument of the book in conceptual terms, namely, the importance of sociability relations to explain the (re)production of poverty. The second chapter has a more descriptive character as it presents the urban structure of the Metropolitan Region of São Paulo and the locations and methodological procedures of the research. The third chapter characterizes the networks of poor individuals and their relation with various attributes, revealing their heterogeneity, and an analysis of the existing similarities but especially the differences in comparison to the social networks of middle-class individuals. The fourth chapter furthers the understanding of heterogeneity concerning the sociability of poor individuals by constructing two typologies (one based on network characteristics and the other on individual's sociability patterns). The fifth chapter discusses the role that networks and sociability play on the social situation of individuals, focusing on how networks mediate the access of individuals to various markets (goods, services, labor etc.). The sixth chapter continues the analysis of the role of networks and sociability, but now focusing on the access to goods and services by non-market means, which operate within the relational webs in which individuals are embedded. The seventh chapter, at last, identifies and analyzes the relational mechanisms that explain the relations observed in previous chapters between the different configurations of individual's social networks (and their changes over time) and poverty conditions marked by significant heterogeneity.

Despite the focus of Eduardo Marques's book being the relationship among poverty, segregation and social networks, the analytical contributions transcend these thematic limits as it is important for the social sciences as a whole. In this sense, what stands out is its theoretical contribution by adopting a relational approach within an academic field where attributes and individual characteristics are still hegemonically understood as central elements (and sometimes the only ones) to construct explanatory models. Without ignoring the importance of such attributes and characteristics, Marques’ analysis highlights the importance of the relational position of individuals for the (re)production of situations of poverty from the argument that “individuals’ access to the structures of opportunities that lead to social conditions in general, and situations of poverty in particular, are mediated by the relational patterns these individuals have with other individuals and with various kinds of organization” (pp.31).

The analytical treatment of this relational dimension of poverty, however, goes beyond the general statement about the importance of social relations for the definition of individuals’ life conditions, which characterizes much of the literature on social capital (especially those adopting a more normative perspective). On the contrary, the author analyzes how different configurations of individuals’ networks (in terms of diameter, homophily, localism etc) form quite heterogeneous structures of opportunities, while also highlighting individual agency and the contingencies, or the diverse uses of those opportunities by individuals.

In this sense, the theoretical perspective built by Marques articulates two dimensions which are traditionally dealt separately: the structural conditions established by the relational positions of individuals; individual agency in being able to identify and take advantage of the opportunities structurally available to them and also the responses to various contingencies (migration, change of residence, death of people within the relationship circle, breaking ties etc) which permeate life trajectories. Thus, Marques’ analysis allows both to identify and analyze the recurring patterns in network configurations, life situations and trajectories of the respondents, and the particularities that comprise the heterogeneous world of poverty.

A second fundamental contribution of Eduardo Marques’ book is within the methodological field. This contribution is particularly relevant to the Brazilian social sciences, which tend to diminish methodological discussion and accuracy based on a misleading association between discussion and rigor with “positivism”. Countering this trend, Marques clearly demonstrates the importance and fruitfulness of a methodological approach which embodies the precepts established by Tilly (2004, pp.6) in his defense of “formalism” in the study of social processes: “Good formalisms make explicit the analyst's claims about relations among the elements under observation. They thereby make those claims available to falsification and modification as a result of comparison with the evidence”.

In Opportunities and Deprivation in the Urban South, then, we find a careful construction of a research problem and the proposal of a complex methodological design oriented to guide an empirical research capable of supporting (or showing the limits of) the arguments constructed and explained by the author. It is noteworthy, in this sense, the combination of quantitative and qualitative methodological procedures, especially the use of Social Network Analysis (SNA), which has been an innovative aspect that characterizes and distinguishes the work of Marques (2000, 2003, 2010).

Regarding specifically the use of SNA, the analysis reveals the limits of this methodology in its current stage of development to apprehend the dynamics of social networks and, in particular, the continuing processes of building and breaking ties throughout the life trajectories of individuals. The static character as “photographs” of the different configurations of networks from the respondents, which are obviously of great analytical value for a number of the research objectives, limits, on the other hand, the understanding of how these networks are formed and transformed over time and also how they are used by individuals in their everyday interactions. To respond to these limitations, the author uses a very successful methodological articulation in which in-depth interviews with selected individuals provide fundamental information about the dynamics of relationship formation and usage filling, thus, the gap left by SNA. At this juncture, the work of Marques besides demonstrating the fruitfulness of a competent applied methodological diversity, points to a potential field of development for SNA as it incorporates a diachronic dimension to understand and analyze social networks.

Finally, the third and, in my opinion, the most significant contribution of Eduardo Marques’ book (especially concerning the Brazilian social sciences) is the incorporation of an approach focused on the identification and analysis of the causal mechanisms (particularly relational and environmental mechanisms) that effectively activate the (re)production of poverty situations. Such a choice places Marques’ book in an important field of epistemological, theoretical and methodological discussions regarding the meaning of causality in social processes, which emerged in the 1990s in the international scenario (Hedström and Swedberg, 1998) but, despite the intense academic debate, have been virtually disregarded in Brazil¹.

The emphasis on causal mechanisms as factors that explain poverty situations distinguishes Marques’ analysis from both the traditional studies observing correlations between variables and attributes and the search for conditions (necessary and/or sufficient) in the (re)production of poverty. Without ignoring attributes or conditions, Marques’ approach apprehends the dynamics, complexity and heterogeneity of the processes that (re) produce poverty situations as they are formed throughout life trajectories that express trends and patterns but are, at the same time, unique.

In this sense, Opportunities and Deprivation in the Urban South is aligned with studies from numerous other authors who adopt the causal mechanisms approach: to develop analyses which do not attempt to build a theoretical model of universal application but rather to identify recurrent causal mechanisms in such processes, producing “different aggregate outcomes depending on the initial conditions, combinations, and sequences in which they occur” (McAdam, Tarrow and Tilly, 2001: 37).

Marques’ book demonstrates this dynamic empirically as recurrent mechanisms are shown to exist in the relational trajectories of the studied individuals (school sociability; professional socialization; costs and efforts of creating and maintaining relationships; relational access to the labor market; association between trust and homophily; organizational insertion/transits). They do not, however, yield a homogeneous result because they depart from different initial conditions, combine themselves in particular ways and operate at different moments in individual trajectories in addition to being activated differently by individuals depending on their specificities and contingencies. The end result is an analysis which, without compromising the causal explanation which enables us to understand the processes of poverty (re)production in general, also addresses the heterogeneity, or even the singularities, that shapes this process.

A point that can be raised, nevertheless, refers to the way the approach of causal mechanisms is presented in Marques’ book, relatively fast and superficially. On the one hand, for readers not familiar with the theme, the explanatory model of Marques may be difficult to understand to the extent that he is challenging the dominant perspectives on causality in the study of social processes. For these readers, there may be lacking a clear understanding of the profound epistemological, theoretical and methodological implications as well as the innovative approach adopted by Marques.

On the other hand, for those familiar with the debate on causal mechanisms in the last decades, I find surprising Marques’ lack of positioning in a field which is characterized by profound disagreements. In particular, the absence of a more elaborate discussion explaining and supporting the author's position concerning one of the main points of that debate: the very definition of causal mechanism (Mahoney, 2003).

The adoption of Tilly's definition by Marques - where mechanisms are “a delimited class of events that alter relations among specified sets of elements in identical or closely similar ways over a variety of situations” (2005, pp.28 - emphasis added) and can be distinguished among environmental, relational and cognitive mechanisms - is fruitful and followed consistently throughout the analysis. Yet, this definition is not the only one possible and can be contrasted, for example, with the definition provided by Machamer, Darden and Craver to whom “mechanisms are entities and activities organized such that they are productive of regular changes from start or set-up to finish or termination conditions” (2000, pp.3 - emphasis added) or Mahoney's definition who conceives mechanisms as “unobserved relations or processes that generate outcomes” (2001, pp.576 - emphasis added). These definitions are not necessarily mutually exclusive but they exemplify the diversity of perspectives (to which many others may be added) to the debate on causal mechanisms that are dismissed by the author.

Regardless of this aspect - which would be pointless if the relative lack of awareness of the debate on causal mechanisms did not apply to a significant share of social scientists (particularly in Brazil) -, all the previously mentioned contributions make the book Opportunities and Deprivation in the Urban South a reference work not only for what it offers in terms of understanding the mechanisms of poverty (re)production in large metropolises, but also because of the compelling research agenda that it establishes for the future.