Theory begins when we put these historically-grounded categories to work to forge new interpretations. We cannot, by this means, hope to explain everything there is, nor even procure a full understanding of singular events. These are not the tasks which theory should address. The aim is, rather, to create frameworks for understanding, an elaborated conceptual apparatus, with which to grasp the most significant relationships at work within the intricate dynamics of social transformation. We can explain as general propositions why technological and organizational change and geographical reorganizations within the spatial division of labour are socially necessary to the survival of capitalism. We can understand the contradictions embedded in such processes and show how the contradictions are manifest within the crisis-prone historical geography of capitalist development. We can understand how new class configurations and alliances form, how they can be expressed as territorial configurations and degenerate into inter-imperialist rivalries. These are the kinds of insights that theory can yield.
The mutual development of theory and of historical and geographical reconstruction, all projected into the fires of political practice, forms the intellectual crucible out of which new strategies for the sane reconstruction of society can emerge. The urgency of that task, in a world beset by all manner of insane dangers - including the threat of all-out nuclear war (an inglorious form of devaluation, that) - surely needs no demonstration. If capitalism has reached such limits, then it is for us to find ways to transcend the limits to capital itself.
From the closing pages (450-1) of David Harvey's The Limits to Capital (1982).