Free trade, intellectually based in
Adam Smith's theory of
division of labor, prevents government from directly restricting
imports and
exports, by eliminating
tariffs and international
currency regulations. Depending on who you talk to, it's either the key to perpetual,
worldwide, economic success, or complete capitulation to the greedy forces of
market globalization.
Worldwide free trade would drastically increase economic efficiency and production, while hurting organized labor in developed countries by shipping more menial tasks overseas. It would become a specialist's world. Among opponents of free trade are: environmentalists who fear greater corporate power may lead to less environmental regulation; humanitarians who worry about the entire third world becoming a first-world production zone; isolationists who don't want their country to take on the economic burdens of others; and communists who despise the spread of pure capitalism in all forms. Opposition to free trade is one of the rare issues on which extreme left-wing and extreme right-wing groups agree, albeit for different reasons.
In essence, the world becomes one market. Whether or not you see this fact as a symbol of global cooperation or global exploitation depends on the filter of your mind more than it depends on the actual theory and its effects. It's a powerful idea, to say the least, and I suggest you read numerous texts on both sides before making up your mind.