Page "Sign" Paragraph 15

Thus there are things which may act as signs without any respect to the human agent ( the things of the external world, all sorts of indications, evidences, symptoms, and physical signals ), there are signs which are always signs ( the entities of the mind as ideas and images, thoughts and feelings, constructs and intentions ); and there are signs that have to get their signification ( as linguistic entities and cultural symbols ).

So, while natural signs serve as the source of signification, the human mind is the agency through which signs signify naturally occurring things, such as objects, states, qualities, quantities, events, processes, or relationships.

Human language and discourse, communication, philosophy, science, logic, mathematics, poetry, theology, and religion are only some of fields of human study and activity where grasping the nature of signs and symbols and patterns of signification may have a decisive value.