Introduction. At this point our study reaches a half-way mark. We first outlined several abstract dimensions by which the structure of any social system may be analysed, and next generated a series of abstract propositions concerning the sequence by which institutionalized activity becomes more differentiated along these dimensions (Chapters I, II). To fill these empty boxes, we described an industry-cotton textiles-in terms of the general dimensions, and re-phrased the abstract propositions of structural change as more specific propositions governing industrial change (Chapter III). Finally, we attempted to assess the workability of these propositions by unravelling the tangled history of structural change in the cotton industry between 1770 and 1840 (Chapters IV-VII). Now we must re-phrase these propositions once more, and apply them to the changes in the economic life of the working-class family in the same period. To carry out these operations on the family economy is to apply the same set of theoretical concepts to a different institutional complex without varying the logic of the theory.