This study of federalism and federation dissects certain problems which have arisen in the description and analysis of the federal form of government. The author does this by applying logical analysis to the necessary elements in the notion of federal union federalism as the expression of a political ideology or ideologies, and federation as an institution or pattern of institutions. He begins by establishing federal ideology as a type of pluralism, which provides the basis for an examination of contrasting interpretations of federalism and then considers the institutions of federation, drawing extensively on empirical examples. The underlying assumption of this work is that it is virtually useless to talk descriptively about institutions without engaging simultaneously in a theoretical analysis of the terms in which this is done.