The primary difference is that Greek classical philosophy focused on metaphysics and ethics, exploring abstract concepts such as the nature of reality and the good life, while Hellenistic philosophy focused more on practical aspects of life, such as how to achieve happiness and tranquility through practices like Stoicism, Epicureanism, and Skepticism. Hellenistic philosophers were more concerned with how individuals could live a fulfilling life in the turbulent times after Alexander the Great's empire fell apart.