ABSTRACT
This chapter explores the idea and concept of the modern constitution and its classifications, evolution, theoretical underpinnings, development and application. It introduces the notions of constitutionalism, constitutional legitimacy and the constitutional development experience and challenges in Africa. A constitution is a distinctive document or set of documents that embody the most important rules about the governance of a modern state. It sets out the framework of the government, postulates how it ought to operate and makes declarations about the purposes of the state and society and the rights and duties of citizen. Kenneth Clinton Wheare has broadly classified the constitution in terms of written versus unwritten; flexible versus rigid; supreme versus subordinate; federal versus confederal versus unitary; presidential-executive versus parliamentary-executive; and republican versus monarchical constitutions. At the foundational level, constitutional theory takes three basic forms, namely positivism, normativism and postmodernism. In political science, the question of what makes a particular regime legitimate is referred to as the problem of legitimacy.
