The philosopher Michalle Gal has offered a moderate version of formalism, entitled "Deep Formalism", which is a symbolic formalism based on philosophical aestheticism. The artwork is defined by her as deep form: "a form steeped in content that cannot be extracted from it. Artistic content, since it has no existence or sense apart from the form, cannot actually be referred to, other than speculatively. The content seals the form in an opaque, non-reflective, productive symbol." Here she introduces a broad concept of symbol, an opaque-productive symbol: one that is not transparent to preconceived or pre-determined referents and meanings, but rather produces new ones.