Freedom, good and evil, love, feminism, success, morality, and chauvinism are abstract concepts. Concrete concepts are those that have physical referents, whereas abstract concepts have none.
Abstract concepts are frequently of interest to philosophers because they raise questions about ontology and sensory experience. Some philosophers, beginning with Plato, have argued that the primary subject of philosophy and metaphysics is abstract concepts.
When analysing the mental and psychological development of children, the issue of abstract versus concrete thought is relevant. Young children are incapable of abstract thought. For example, according to the Brain Injury Association of New York State, a 2- or 3-year-old child who reads “Green Eggs and Ham” by Dr. Seuss is typically only able to comprehend the story concretely as that of a person who does not want to eat green eggs and ham and may understand that the story is about a person changing his mind. The story is about the abstract notion that people can change their thoughts and emotions even when they do not believe they can. A child will be able to comprehend this abstract concept if an adult discusses it with him, bringing him closer to understanding abstract concepts.