Democritus (c. 460 – c. 370 BCE) was an ancient Greek philosopher best known for his pioneering work in the development of atomism, the theory that matter is composed of small, indivisible particles called atoms. He is often referred to as the "laughing philosopher" due to his emphasis on cheerfulness and his belief that happiness is attainable through knowledge and wisdom.
Democritus posited that everything in the universe is made up of atoms, which are eternal, unchangeable, and vary in shape and size, thereby accounting for the diversity of substances and phenomena in the natural world. His ideas were part of the broader pre-Socratic philosophical landscape and contributed significantly to the later development of scientific thought.
Much of what we know about Democritus comes from the writings of later philosophers, particularly Aristotle, who critiqued some of his ideas. Despite this, Democritus’s thoughts laid important groundwork for modern atomic theory and influenced subsequent philosophers and scientists, including Epicurus and, eventually, contemporary scientists in the field of chemistry and physics.