If a thought or idea exists in the mind, it is real. Realism is the second oldest school of philosophy. Realists believe your mind can imagine things that don't exist and it is possible to arrive at incorrect conclusions through mental reasoning. Therefore, realists reject idealism and believe what is real is what is actually experienced. By studying actual objects and naturally occurring phenomena, we learn the truth.
Realists favor the sciences.
Realism didn't catch on until the 1600s. A realist would carefully study the materials in a chair and subject them to a variety of tests to learn as much as possible about the materials. A realist would also weigh and measure the chair and even analyze the finish. Pragmatism is a philosophy that emerged during the later part of the 1800s. Pragmatists do not believe in knowledge for the sake of knowledge or science for the sake of science.