> A PhD is ultimately like any other degree: a school programme where, at the end, some instituting is staking part of its reputation on giving the world a prom

> A PhD is ultimately like any other degree: a school programme where, at the end, some instituting is staking part of its reputation on giving the world a promise that you have some minimum competence in some field. Anything you learn in school, you can in principle learn on your own. No, this neglects perhaps the most important aspect of a PhD: it is an apprenticeship with a professional researcher. Learning through apprenticeship is the most ancient and still often most effective methods of learning complicated skills. It is reasonable to dispute the value of accreditation from a university -- that's a practical question, and indeed strict university accreditation is relatively modern -- but it's not reasonable to think that anything you can learn in "school" can be learned on your own.