Materialism is a philosophical position that states that everything in existence is composed of physical matter and therefore subject to the laws of physics. It states that physical matter comprises everything in the universe and all things, even mental processes and consciousness, results from matter and its movement. Materialists deny the existence of spiritual or mental concepts. Everything in the universe can be explained by physical matter. This philosophical stand-point were first introduced in the time of the ancients but gained new momentum when the scientific revolution started in the 17th century. Many modern philosophers claim to be materialists.