Creating lies for a living.
Good design is necessary because it enables the creation of artifacts and concepts that can perform in an imperfect and chaotic world.
Of course, this doesn’t mean that everyone is a designer. At least not purposefully. Design is factual, but not everyone is a good designer, and that’s why people like me still have a job.
…is pure application. You won’t see anything about golden ratios. I don’t even mention color theory. Only what I’ve learned from being bad and then deliberately practicing.