Aristotle is most commonly credited with formulating the building blocks of deductive logic, basic ethical and moral guidelines and laying the foundations for the biological classifications of animals. Although basic by the standards of modern science, Aristotle's classification was used for hundreds of years, and his philosophical work is still discussed today.
Aristotle produced a number of texts outlining basic scientific enquiries, particularly in meteorology, which Aristotle defined as the study of the earth, water and natural events, as well as astronomical ones.
Aristotle's philosophical goal was to create a system of enquiry by which all men could eventually learn all there is to know about the world. This formed the basis of his systematic and deductive concept of logic.
Some of Aristotle's most accurate pre-scientific observations are found in his studies of marine biology. These proved to be far more accurate than his ideas about biology (which simply categorized animals as those with red blood and those without), perhaps in part because he performed thorough examinations of anatomy through dissection.
He also introduced the concept of metaphysics to philosophy, which went on to be discussed at length by many following philosophers, becoming a central part of the discipline itself.