A logic with normal modal operators and countable infinite conjunctions and disjunctions is introduced. A Hilbert's style axiomatization is proved complete for this logic, as well as for countable sublogics and subtheories. It is also shown that the logic has the interpolation property.

The irreducibility thesis -- The facticity of practices -- Constructing practice theory through double hermeneutics -- The trans-subjectivity of social practices -- The dialogical self as thrown projection in practices -- Epilogue -- Bibliography -- Index.