Philosophical Transactions later Philosophical Transactions of the Royal Society (Phil. Trans.) is a scientific journal published by the Royal Society. In its earliest days, it was a private venture of the Royal Society's secretary. It became an official society publication in the eighteenth century. It was established in 1665, making it the first journal in the world exclusively devoted to science, and therefore also the world's longest-running scientific journal. The use of the word "Philosophical" in the title refers to "natural philosophy", which was the equivalent of what would now be generally called "science".