therefore, after the Middle Ages, allowed itself to be overtaken by the West and then dropped further and further behind (his answer is discussed on pages 323-324).4 The same might be said about Islam. Baghdad in the ninth century led the Mediterranean world intellectually: it was here that the great classics of the ancient civilisations were translated, where the hospital was conceived, where al-jabr , or algebra, was developed, and major advances made in falsafah . By the eleventh century, thanks to the rigours of fundamentalism, it had disappeared. Charles Freeman, in his recent book The Closing of the Western Mind , describes many instances of the way intellectual life withered in the early Middle Ages, the years of Christian fundamentalism.5 In the fourth century Lactantius wrote: 'What purpose does knowledge serve-for as to knowledge of natural causes, what blessing is there for me if I should know where the Nile rises, or whatever else under the heavens the "scientists" rave about?'6 Epilepsy, which Hippocrates described as a natural illness as early as the fifth century BC, was, in the Middle Ages, placed under the care of St Christopher. John of Gaddesden, an English physician, recommended as a cure the reading of the Gospel over the epileptic while simultaneously placing on him the hair of a white dog.7 This is perhaps the most important lesson we can learn from a history of ideas: that intellectual life- arguably the most important, satisfying and characteristic dimension to our existence-is a fragile thing, easily destroyed or wasted. In the last chapter some conclusions will be attempted, in an effort to assess what has and has not been achieved in this realm. This Introduction, however, shows how this history differs from other histories, and in so doing helps explain what a history of ideas is . The discussion will be confined to an exploration of the various ways the material for an intellectual history may be organised. A history of ideas clearly touches on a vast amount of material and ways must be found to make this array manageable. For some reason, numerous figures in the past have viewed intellectual history as a tripartite system- organised around three grand ideas, ages or principles. Joachim of Fiore ( c . 1135-1202) argued- heretically-that there have been three epochs, presided over by God the Father, God the Son and God the Holy Spirit respectively, during which the Old Testament, the New Testament and a 'spiritual eternal Gospel' will be in force.8 Jean Bodin ( c . 1530-1596), the French political philosopher, divided history into three periods-the history of Oriental peoples, the history of Mediterranean peoples, and the history of northern peoples.9 In 1620 Francis Bacon identified three discoveries that set his age apart from ancient times.10 'It is well to observe the force and virtue and consequences of discoveries. These are to be seen nowhere more conspicuously than in those three which were unknown to the ancients, and of which the origin, though recent, is obscure and inglorious; namely, printing, gunpowder, and the magnet. For these three have changed the whole face and state of things throughout the world, the first in literature, the second in warfare, the third in navigation; whence have followed innumerable changes; insomuch that no empire, no sect, no star, seems to have exerted greater power and influence in human affairs than these mechanical discoveries.'11 The origins of each of these discoveries have been identified since Bacon's time but that does not change the force of his arguments. Thomas Hobbes (1588-1679), Bacon's amanuensis, argued that three branches of knowledge outweighed all others in explanatory power: physics, which studies natural objects; psychology, which studies man as an individual; and politics, which deals with artificial and social groupings of mankind. Giambattista Vico (1668-1744) distinguished the age of the gods, the heroic age and the human age (though he borrowed some of these ideas from Herodotus and Varro). In fact, Vico tended to think in threes: he distinguished three 'instincts' which, he said, shaped history, and three 'punishments' that shaped civilisation.12 The three instincts were a belief in Providence, the recognition of parenthood, and the instinct to bury the dead, which gave mankind the institutions of religion, family and sepulture.13 The three punishments were shame, curiosity and the need to work.14 The French statesman Anne Robert Jacques Turgot (1727- 1781) argued that civilisation is the product of geographical, biological and psychological factors (Saint-Simon agreed). Marie Jean Antoine Nicolas Caritat, marquis de Condorcet (1743-1794), who thought that the French Revolution was the dividing line between the past and a 'glorious future', believed there were three outstanding issues in history-the destruction of inequality between nations, the progress of