I call ‘strategy’ the calculus of force-relationships which become possible when a subject of will and power (a proprietor, an enterprise, a city, a scientific institution) can be isolated from an environment. A strategy assumes a place that can be circumscribed as proper (propre) and thus serve as the basis for generating relations with an exterior distinct from it (competitors, adversaries, ‘clientèles’, ‘targets’ or ‘objects’ of research). Political economic and scientific rationality has been constructed on this strategic model.
I call a ‘tactic’, on the other hand, a calculus which cannot count on a ‘proper’ (a spatial or institutional localization), nor thus on a borderline distinguishing the other as a visible totality. The place of a tactic belongs to the other. A tactic insinuates itself into the other’s place, fragmentarily, without taking it over in its entirety, without being able to keep it at a distance. It has at its disposal no base where it can capitalize on its advantages, prepare its expansions, and secure independence with respect to circumstances. The proper is a victory of space over time. On the contrary, because it does not have a place, a tactic depends on time – it is always on the watch for opportunities that must be seized ‘on the wing’. Whatever it wins, it does not keep. It must constantly manipulate events in order to turn them into ‘opportunities’.

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The practise of everyday life van Michel de Certeau, 1984