At some point in the history of sociology there was a transition from the founding non-professional genius to the professional disciplinary researcher. Marx and Tocqueville certainly fall in the former category; Robert Merton, Mayer Zald, and Neil Smelser fall clearly in the latter. By some time in the mid-twentieth century sociology had become "professionalized." What is the situation of the "professional" sociologist? To what extent and why is this an improvement? And where do Durkheim and Weber fall in this transition?
We might characterize a discipline as --
a complex set of social institutions that organize, validate, and evaluate the work products of knowledge seekers.This means several things: organized processes for identifying and ranking important research problems; institutions for selecting and training young scientists; formal processes for evaluating scientific work; institutions for valorizing and disseminating scientific results; and ways of prioritizing certain methods of knowledge formation and discouraging others. As Andrew Abbott shows in Department and Discipline: Chicago Sociology at One Hundred.)
So now let's return to the cases of Tocqueville and Durkheim. How do these beacons of French sociology fare on the spectrum of the academic professions? Tocqueville is the easier case. He was an innovative and rigorous thinker when it came to understanding the social world around him. But he was clearly not a "professional," for several reasons. He was not immersed in an evaluative framework in the context of which his scientific work was to be judged. His research questions were of his own design, not part of an active community of sociologists with considered judgments about what topics were important. His reasoning about society and history followed his own intuitions about inference and explanation, not a community-based set of norms dictating answers to these questions. There was no professional discipline of sociology in 1835, and Tocqueville was not a professional.
The case of Durkheim is a bit more difficult. (Steven Lukes's Emile Durkheim: His Life and Work: A Historical and Critical Study is a superb critical discussion of Durkheim's intellectual development (google books). Robert Nisbet's The Sociology of Emile Durkheim is also valuable.) Durkheim was highly credentialed, with degrees from the École Normale Supérieure -- and of course credentialing is a crucial component of professionalization. At the same time he was a founder; he was a highly original thinker with his own intuitions about what society consists of and how to research it. This implies that he was a "genius founder" or a sui generis amateur. But he was also embedded within a tradition of thought that was beginning to look more like an emerging discipline of sociology. His thought fit logically and clearly -- albeit with originality -- into a tradition of teachers and writers like Fustel de Coulanges and Hyppolite Taine -- another mark of being part of a discipline or research tradition. And he distinguished himself from Comte and Spencer by committing himself to specialized studies of particular social phenomena -- yet another sign of professionalism (Lukes, 137-38; 289).
And what about publications and external standards of quality assessment? Here again, Durkheim was on the cusp of a transition. He himself was the creator and long-time editor of one of the first sociological journals in 1896, L'Année Sociologique. His goal was to establish a working collaboration of young sociologists to contribute to the progress and specialization of the new science of sociology. Other young sociologists associated with the journal included Célestin Bouglé, Marcel Mauss, Henri Hubert, Robert Hertz, Maurice Halbwachs, and François Simiand. Durkheim was a prolific reviewer of other people's academic work in the journal (a discipline-like activity), and he did so on the basis of standards that were clearly sociological. And of course he published numerous important and influential books on different aspects of social order, and these books helped to set the research agenda for French sociology for the next generation -- yet another disciplinary activity.
So perhaps we can say that Durkheim played a dual role with respect to sociology as a professional social science. He both contributed to the definition and articulation of a discipline of sociology, and he also fell within that discipline. He was a professional sociologist in the somewhat unusual sense that Bob "Barky" Barkhimer was a professional NASCAR driver: he helped to create the very institutional processes and institutions that would eventually validate his work.