Who made us think the way we do?
The so-called 'Father of Modern Philosophy', this 17th century Frenchman not only pioneered analytical geometry, but also famously said 'I think therefore I am', a profound statement whose core principle sparked more modern movements such as Existentialism and Post-modernism in acknowledging that reality, first and foremost, sits within the individual and is formulated through the lens of an individual's experience.
The most important philosopher in Eastern thought, without a doubt. A rough contemporary of Ancient Greek philosophers, he dissected codes of ethics and politics just as they did, and reached many of the same conclusions. He advocated a system of government centered around the 'morality of the people', and acknowledged that pure monarchy was a poor system of government - but a monarch who was accountable, respected and open to his people (and had limited power) was an okay thing. One of his most fundamental contributions to humanity was in his formulation of the Eastern version of the Golden Rule ("do unto others..."), his ran like this: "What one does not wish for oneself, one ought not to do to anyone else; what one recognizes as desirable for oneself, one ought to be willing to grant to others."
His full name was Abu ʿAli al-Ḥusayn ibn ʿAbd Allah ibn Sina: a Persian philosopher and physician, whose philosophy was closely informed by nature. He was the first person to pinpoint and codify the five senses, and one of the first people to look for medical explanations for psychiatric disorders, instead of dismissing the mentally ill as 'possessed'. He codified scientific and philosophical reasoning and logic, which was the basis for the scientific method. His less ground-breaking observations include theorizing that Venus was closer to the Sun than the Earth, an extraordinary and contradictory belief at the time.
2. John Locke
Another 'Father', this time of modern political and social thought. He espoused individual freedom above all else, and universal equality before the law. His three 'Natural Rights', shared by all beings - life, liberty, and estate - are forever enshrined in the US Declaration of Independence as "life, liberty and the pursuit of happiness", originally "life, liberty and the pursuit of property" before it was changed in the final, ratified version to appear more palatable. His ideas informed other key liberalist thinkers like Thomas Jefferson, Abraham Lincoln and John Stuart Mill (arguably the first Feminist), who in turn helped form modern democracy; and spurred revolutionaries everywhere, from late 18th century France to 60s Africa, Asia and South America to seek that liberté, egalité, fraternité. A true giant.
1. Plato / Socrates
Overshadowing all these greats (with the exception of Confucius) are two people from Athens, a tutor and his tutee. Now, I know the title of this article is the 5 most influential philosophers, but in this case Plato and Socrates pretty much function as the same person. Why? Because while Socrates taught Plato everything he knew, it was Plato who wrote it down and developed it further. Indeed, Plato uses Socrates as a mouthpiece for his ideas, even after Socrates died. But how did they innovate, I hear you ask? To put it simply, they invented Western philosophy as a discipline. As the expression goes, "all philosophy is footnotes on Plato", and not without reason. In fact, the footnotes began being written during his lifetime, with his student Aristotle (who some of you may be annoyed isn't on this list - sorry!), who was a philosophical giant in his own right. As a duo, they questioned the nature of existence, the structure of society, forms of government and what constituted 'real'. Interestingly, they didn't support democracy (ironic, given that they lived in the first democratic state) - they believed the freedom afforded by democracy wasn't true freedom - but advocated instead for benevolent dictatorship by philosopher-kings.