Vitalism is a philosophical theory that suggests living organisms are fundamentally different from inanimate objects because they possess a vital force or energy. This concept implies that life cannot be fully explained by physical and chemical processes alone, as there is an essential quality that distinguishes living beings. Historically, vitalism was prominent in the 18th and 19th centuries, influencing thinkers like Henri Bergson and Aristotle. However, with advancements in biology and the development of the cell theory, vitalism has largely fallen out of favor in the scientific community, as many life processes can now be explained through biochemical mechanisms.