384 BC–322 BC Greek philosopher Aristotle, a pupil of Plato and the tutor of Alexander the Great, authored works on ethics, natural sciences, politics, and poetics that profoundly influenced western thought; empirical observation precedes theory, and the syllogism bases logic, the essential method of rational inquiry in his system, which led him to see and to criticize metaphysical excesses. German religious philosopher Saint Albertus Magnus later sought to apply his methods to current scientific questions. Philosophy of Saint Thomas Aquinas, the most influential thinker of the medieval period, combined doctrine of Aristotle within a context of Christianity. Aristotle numbers among the greatest of all time. Almost peerless, he shaped centuries from late antiquity through the Renaissance, and people even today continue to study him with keen, non-antiquarian interest. This prodigious researcher and writer left a great body, perhaps numbering as many as two hundred treatises, from which 31 survive. His extant writings span a wide range of disciplines from mind through aesthetics and rhetoric and into such primary fields as biology; he excelled at detailed plant and animal taxonomy. In all these topics, he provided illumination, met with resistance, sparked debate, and generally stimulated the sustained interest of an abiding readership. Wide range and its remoteness in time defies easy encapsulation. The long history of interpretation and appropriation of texts and themes, spanning over two millennia within a variety of religious and secular traditions, rendered controversial even basic points of interpretation.

Aelius Galenus or Claudius Galenus (AD 129–c. 200/c. 216), better known as Galen of Pergamon (modern-day Bergama, Turkey), was a prominent Roman (of Greek ethnicity) physician, surgeon and philosopher. Arguably the most accomplished of all medical researchers of antiquity, Galen contributed greatly to the understanding of numerous scientific disciplines, including anatomy, physiology, pathology, pharmacology, and neurology, as well as philosophy and logic. The son of Aelius Nicon, a wealthy architect with scholarly interests, Galen received a comprehensive education that prepared him for a successful career as a physician and philosopher. He traveled extensively, exposing himself to a wide variety of medical theories and discoveries before settling in Rome, where he served prominent members of Roman society and eventually was given the position of personal physician to several emperors. Galen's understanding of anatomy and medicine was principally influenced by the then-current theory of humorism, as advanced by many ancient Greek physicians such as Hippocrates. His theories dominated and influenced Western medical science for more than 1,300 years. His anatomical reports, based mainly on dissection of monkeys, especially the Barbary Macaque, and pigs, remained uncontested until 1543, when printed descriptions and illustrations of human dissections were published in the seminal work De humani corporis fabrica by Andreas Vesalius where Galen's physiological theory was accommodated to these new observations. Galen's theory of the physiology of the circulatory system endured until 1628, when William Harvey published his treatise entitled De motu cordis, in which he established that blood circulates, with the heart acting as a pump. Medical students continued to study Galen's writings until well into the 19th century. Galen conducted many nerve ligation experiments that supported the theory, which is still accepted today, that the brain controls all the motions of the muscles by means of the cranial and peripheral nervous systems. Galen saw himself as both a physician and a philosopher, as he wrote in his treatise entitled That the Best Physician is also a Philosopher. Galen was very interested in the debate between the rationalist and empiricist medical sects, and his use of direct observation, dissection and vivisection represents a complex middle ground between the extremes of those two viewpoints. Many of his works have been preserved and/or translated from the original Greek, although many were destroyed and some credited to him are believed to be spurious. Although there is some debate over the date of his death, he was no younger than seventy when he died.

Diogenes of Sinope (Greek: Διογένης ὁ Σινωπεύς, Diogenēs ho Sinōpeus) was a Greek philosopher and one of the founders of Cynic philosophy. Also known as Diogenes the Cynic (Ancient Greek: Διογένης ὁ Κυνικός, Diogenēs ho Kunikos), he was born in Sinope (modern-day Sinop, Turkey), an Ionian colony on the Black Sea, in 412 or 404 BCE and died at Corinth in 323 BCE. Diogenes of Sinope was a controversial figure. His father minted coins for a living, and when Diogenes took to debasement of currency, he was banished from Sinope. After being exiled, he moved to Athens to debunk cultural conventions. Diogenes modelled himself on the example of Hercules. He believed that virtue was better revealed in action than in theory. He used his simple lifestyle and behaviour to criticise the social values and institutions of what he saw as a corrupt society. He declared himself a cosmopolitan. There are many tales about him dogging Antisthenes' footsteps and becoming his faithful hound. Diogenes made a virtue of poverty. He begged for a living and slept in a large ceramic jar in the marketplace. He became notorious for his philosophical stunts such as carrying a lamp in the daytime, claiming to be looking for an honest man. He embarrassed Plato, disputed his interpretation of Socrates and sabotaged his lectures. Diogenes was also responsible for publicly mocking Alexander the Great. After being captured by pirates and sold into slavery, Diogenes eventually settled in Corinth. There he passed his philosophy of Cynicism to Crates, who taught it to Zeno of Citium, who fashioned it into the school of Stoicism, one of the most enduring schools of Greek philosophy. None of Diogenes' many writings has survived, but details of his life come in the form of anecdotes (chreia), especially from Diogenes Laërtius, in his book Lives and Opinions of Eminent Philosophers. All we have is a number of anecdotes concerning his life and sayings attributed to him in a number of scattered classical sources. Diogenes was born in the Greek colony of Sinope on the south coast of the Black Sea, in either 412 BC or 404 BCE. Nothing is known about his early life except that his father Hicesias was a banker. It seems likely that Diogenes was also enrolled into the banking business aiding his father. At some point (the exact date is unknown), Hicesias and Diogenes became embroiled in a scandal involving the adulteration or debasement of the currency, and Diogenes was exiled from the city. This aspect of the story seems to be corroborated by archaeology: large numbers of defaced coins (smashed with a large chisel stamp) have been discovered at Sinope dating from the middle of the 4th century BCE, and other coins of the time bear the name of Hicesias as the official who minted them. The reasons for the defacement of the coinage are unclear; Sinope was being disputed between pro-Persian and pro-Greek factions in the 4th century, and there may have been political rather than financial motives behind the act. It was in Corinth that a meeting between Alexander the Great and Diogenes is supposed to have taken place. The accounts of Plutarch and Diogenes Laërtius recount that they exchanged only a few words: while Diogenes was relaxing in the sunlight in the morning, Alexander, thrilled to meet the famous philosopher, asked if there was any favour he might do for him. Diogenes replied, "Yes, stand out of my sunlight". Alexander then declared, "If I were not Alexander, then I should wish to be Diogenes", to which Diogenes replied, "If I were not Diogenes, I should also wish to be Diogenes." In another account of the conversation, Alexander found the philosopher looking attentively at a pile of human bones. Diogenes explained, "I am searching for the bones of your father but cannot distinguish them from those of a slave."

Publius Ovidius Naso (20 March 43 BCE – CE 17/18), known as Ovid (/ˈɒvɪd/) in the English-speaking world, was a Roman poet best known for the Metamorphoses, a 15-book continuous mythological narrative written in the meter of epic, and for collections of love poetry in elegiac couplets, especially the Amores ("Love Affairs") and Ars Amatoria ("Art of Love"). His poetry was much imitated during Late Antiquity and the Middle Ages, and greatly influenced Western art and literature. The Metamorphoses remains one of the most important sources of classical mythology. Ovid is traditionally ranked alongside Virgil and Horace, his older contemporaries, as one of the three canonic poets of Latin literature. He was the first major Roman poet to begin his career during the reign of Augustus, and the Imperial scholar Quintilian considered him the last of the Latin love elegists. He enjoyed enormous popularity, but in one of the mysteries of literary history he was sent by Augustus into exile in a remote province on the Black Sea, where he remained until his death. Ovid himself attributes his exile to carmen et error, "a poem and a mistake", but his discretion in discussing the causes has resulted in much speculation among scholars. Ovid's prolific poetry includes the Heroides, a collection of verse epistles written as by mythological heroines to the lovers who abandoned them; the Fasti, an incomplete six-book exploration of Roman religion with a calendar structure; and the Tristia and Epistulae ex Ponto, two collections of elegies in the form of complaining letters from his exile. His shorter works include the Remedia Amoris ("Cure for Love"), the curse-poem Ibis, and an advice poem on women's cosmetics. He wrote a lost tragedy, Medea, and mentions that some of his other works were adapted for staged performance. See also Ovide.