A related debate centers on the distinction between “knowledge” and “skills,” and how schools and teachers may interpret—or misinterpret—the concepts. Some educators argue that it’s not possible to teach cross-disciplinary skills separately from knowledge and conceptual understanding—for example, students can’t learn to write well if they don’t have ideas, facts, principles, and philosophies to write about. The basic idea is that “21st century skills” is an artificial concept that can’t be separated out from subject-area knowledge and instruction. Other educators may argue that cross-disciplinary skills have historically been ignored or under-prioritized in schools, and the push to give more emphasis and attention to these skills is simply a commonsense response to a changing world.