“Speculation occurs when people buy assets, always with the support of some rationalizing doctrine, because they expect their prices to rise. That expectation and the resulting action then serve to confirm expectation. Presently the reality is not what the asset in question—the land or commodity or stock or investment company—will earn in the future. Rather it is only that enough people are expecting the speculative object to advance in price to make it advance in price and thus attract yet more people to yet further fulfill expectations of yet further increases.”
-John Galbraith in his book Money: Whence It Came, Where It Went (page 124)