Great People

§ Time and again through history, there have arisen men and women who have profoundly changed the world around them - artists, scientists, prophets and others whose genius sets them head and shoulders above the rest. In Civilization IV, such visionaries are called "Great People."
§ There are five different kinds of great people in the game: Great Prophets, Great Merchants, Great Artists, Great Scientists, and Great Engineers. Each has a special ability.
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Generating Great People

§ Great people are generated in cities. Each city generates a separate pool of "great people points" - when the city has earned enough points, it will generate a great person. The cost of generating a great person escalates throughout the game: the first great person costs 100 great people points, the second costs 200, and so forth. (The number of points needed to produce a great person is different on the Quick and Epic game speeds.)
§ The first civilization to discover certain technologies will also receive a free great person in their capital city. For example, the first civ to discover Music receives a Great Artist.
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Great People Points

§ A city generates great people points in a number of ways: by constructing Wonders, by assigning citizens to be specialists, and by choosing certain Civics.
§ Wonders: A wonder will generate a certain number of great people points each turn. Further, some wonders can increase a city's (or entire civilization's!) great people point generation significantly (see the Parthenon for an example). Like specialists (see next), some wonders increase the chances of generating a specific type of great person in their city.
§ Specialists: In each City you can assign citizens to be "specialists." Each specialist provides some kind of production bonus to its city; in addition, most generate great people points (the citizen specialist being the sole exception). Further, the kinds of specialists you have in a city determine which great people you generate: if all of your specialists in a city are priests, when that city generates a great person, he or she will be a great prophet. If half the specialists are merchants and the other half artists, you'll have a fifty-fifty chance of generating a great artist or great merchant.Moving the mouse over the great person points bar will display the percentage of getting each type of great person.
§ Civics: Some Civics increase the speed at which you generate great people.
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Great People Characterists

§ As mentioned above, there are five types of great people. Each type has its own special abilities, but they all share some characteristics:
§ Can Discover New Technologies: You can expend a great person to discover a new technology. Typically this technology will be in the great person's area of expertise (prophets will usually discover religious technologies and so on), but not always. Once all of the relatively inexpensive technologies have been discovered, the great person may not be able to entirely discover a new tech, but he or she can dramatically decrease the time it takes you to discover it.
§ Golden Ages: You can expend two or more great people to start a "Golden Age"; see that section for more details.
§ Settling in Cities: All great persons also have the ability to settle in a city as a sort of "super-specialist". Settling a great person in a city will add certain bonuses to that city each turn; for example, a Great Prophet will add 2 production and 5 gold to the city it settles in.
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Special Abilities

§  In addition to their common abilities, each great person type has other unique abilities.
§ Great Artists: Great Artists can create great works of art in a city; this immediately gives that city additional Culture points (from 2,000 to 6,000, depending upon game speed). This is extremely useful if a city is under cultural threat from a neighbor (or you wish to culturally attack those cities!). Great Artists can also "permanently settle" in a city, providing a continuing large cultural and small research boost to the city.
§ Great Engineers: Great Engineers can "hurry" a city's production, greatly speeding up the creation of whatever the city is presently constructing. Most early wonders can be completed in a single turn by Great Engineers, and later ones can be sped up dramatically. Great Engineers can permanently settle in a city, providing a continuing large production and small research boost to that city.
§ Great Merchants: A Great Merchant can conduct a "trade mission" which will immediately give you a whole bunch of gold. To conduct a trade mission, first move the merchant to a wealthy and powerful city as far away from your cities as possible. When the merchant reaches the target city you'll be able to conduct the mission; trade missions can ONLY be carried out in foreign cities. The value of the mission increases the further away and wealthier the target city is. Great Merchants can also settle permanently in a city, providing a continuing large commerce and small food boost to the city.
§ Great Prophet: Great Prophets can create religious shrines - the Temple of Solomon and the Kong Miao, for example. However, Great Prophets can create religious shrines ONLY in a city where a religion was founded. Using a Great Prophet is the only way to build a religion's shrine. Great Prophets can also settle in a city, providing a continuing large commerce and small production boost to that city.
§ Great Scientist: Great Scientists can construct an Academy, a building which greatly boots a city's scientific research as well as its culture. Great Scientists can also settle permanently in a city, providing a large research and small production boost to the city.