Gómez Pereira (1500–1567) was a Spanish philosopher, doctor, and natural humanist from Medina del Campo. Pereira worked hard to dispel medieval concepts of medicine and proposed the application of empirical methods; as for his philosophy, it is of the standard direction and his reasonings are a clear precedent of René Descartes. He was the first to propose the famous "Cogito ergo sum", in 1554, commonly attributed to Descartes. He was famous for his practice of medicine, although he had many diverse occupations, such as owning businesses, engineering, and philosophy. Biography Not much is known of his life, because there was no one who took care of his manuscripts. What is known is the result of the investigation of unrelated documents to which researchers have given shape, many of them having to do with business or lawsuits. Born in 1500 in Medina del Campo, he was the second of five brothers; his father, Antonia Pereira, owned a small shop of " xerguería," i.e., fabrics and low quality cloths. His mother, Margarita de Medina, died in 1515 and her sons went to the care of her aunt Ana de Avila. It is thought that Pereira descended from a family of converted Jews originally from Portugal, though this is not certain because the source of this was a neighbor that testified against him in a lawsuit. However, we cannot rule out this conversion because we know that, until his marriage, Pereira lived with his parents on Serrano street, which is located in the old Jewish quarter of town. Pereira studied natural philosophy at the University of Salamanca with professor Juan Martínez Silíceo (who later became the archbishop of Toledo between 1545 and 1557). There, apparently, he was actively involved in the disputes between the realists and the nominalists, preferring the latter and rejecting the authority of the old masters in favor of knowledge provided by experience and reason. Here, he also studied medicine, concluding his studies 1520. He then returned to Medina where he established himself as a doctor. He married Isabel Rodriguez and lived on Rúa Nueva (now Padilla Street) where he worked as a doctor and managed the business that he inherited from his family. He possessed a considerable amount of capital and invested in a wide range of business including responsibility for making the actual income and managing the collection of several parishes, trading and warehousing wines, and renting rooms