Aristotle apparently lectured on a wide variety of topics, many of which had never been studied before, making him an innovator. He often lectured repeatedly on the same topic, contiuously improving on his own thought processes, writing down his lectures, many of which we still have today. Some of his topics included logic, physics, astronomy, meteorology, zoology, metaphysics, theology, psychology, politics, economics, ethics, rhetoric, and poetics.
Today, there exists some debate on whether the works we recognize as Aristotle's were all written by him or his followers. However, some explain the difference in writing style as the development over the years of his own beliefs.
While Aristotle's contributions in each subject were considerable for the time, his major contribution was to the overall study and teaching of such subjects, many of which had never been considered before. Two areas which he advanced, which are of particular interest to readers of this site were physics and astronomy. He made very interesting discussion os the topics of matter, change, movement, space, position, and time as well as studying comets.