Louis-Antoine Léon de Saint-Just (1767-1794) was a revolutionary, a statesman, and a political philosopher, yet it is largely only as a revolutionary that he is remembered. As a political person who occupied these three different but overlapping roles, Saint-Just is ideal as the subject and center of a study of actualization, the taking of political ideals into reality. Saint-Just’s political philosophy was that of an idealist, and yet he, by force of circumstance, ability, and audacity, had the opportunity in his short life to attempt to establish and put into practice his political ideals. In his work as a political person Saint-Just created templates for the understanding of the relationship between political theory and political action. Saint-Just’s political theory is examined in relation to his political action, using the concepts of ‘the natural’, ‘the civil’, ‘the social’ and ‘the political’, concepts which are central in Saint-Just’s political philosophy. Saint-Just’s formulations of these concepts, concepts which have also been central to the history of political philosophy, and his understanding of the relations between these concepts, helps to establish him as a political philosopher of some importance, as does the theory and practice approach to politics which his attempts demanded and which his political life demonstrated. In Saint-Just’s function as political philosopher the thesis finds the theoretical element of politics, which becomes redefined in its interaction with Saint-Just’s other functions as statesman and revolutionary, the latter two of which correspond roughly to practice and exigency. As a theorist who is also a statesman in a context of exigency, or revolution, Saint-Just’s political life is a constantly rearranged juxtaposition of theory, practice, and revolution, albeit one which never loses it essential ties to its philosophical base, even in the hours of greatest emergency. Such dedication to a philosophical base, one which refuses to dispense with political philosophy, demonstrates a new conception of political philosophy for the modern world, fills in elements of a theory of revolution as a phenomenon of both theory and action, and provides a contained case for examination of political philosophy and political action, questioning their disunity.