Xenocrates (/zəˈnɒkrəˌtiːz/; Greek: Ξενοκράτης; c. 396/5 – 314/3 BC) of Chalcedon was a Greek philosopher, mathematician, and leader (scholarch) of the Platonic Academy from 339/8 to 314/3 BC. His teachings followed those of Plato, which he attempted to define more closely, often with mathematical elements. He distinguished three forms of being, the sensible, the intelligible, and a third compounded of the two, to which correspond respectively, sense, intellect and opinion.