Born at Stagira in northern Greece, Aristotle is the only philosopher of the ancient world to rival Plato in importance. Aged 17, he became a student at Plato’s Academy, where he remained until Plato’s death twenty years later. Aristotle then left Athens, but later returned to found his own school there, the Lyceum. At the Lyceum was the “peripatos”, the covered walk, after which Aristotle’s followers, the Peripatetics, were named. Like Socrates before him, Aristotle’s life ended with a charge of impiety, though Aristotle, unlike Socrates, chose to flee rather than to face his fate; he died a year later.

Only some of Aristotle’s works survive, most through a first-century BC collection compiled from the records of the Lyceum by Andronicus of Rhodes. His corpus covered a wide range of disciplines, from philosophy and rhetoric to physics and biology. His greatest work, though, was that on metaphysics, logic, and ethics.

St Thomas Aquinas, whose Summa Theologica is the single most important work of theology, was profoundly influenced by Aristotle. Indeed, the Summa can be seen as a synthesis of Aristotelian philosophy with Christian doctrine. Several decades before Aquinas started this work, the Council of Paris had threatened ex-communication to anyone studying Aristotle; indeed following Aquinas’s death his thought was initially rejected by the Church. Soon, though, both Aquinas and Aristotle were accepted, no longer seen as heretics but instead providing the foundation for much orthodox theology.