I wanted to take a moment to share some excerpts from David Deutsch's The Beginning of Infinity (a New York Times bestseller). This is one of my favorite books. I think it has some flaws, but in it David Deutsch eloquently presents a lot of essential ideas better than anywhere else I've encountered.
In it, he defines bad philosophy as "philosophy that is not merely false, but actively prevents the growth of other knowledge."
"Error is the normal state of our knowledge, and is no disgrace. There is nothing bad about false philosophy. Problems are inevitable, but they can be solved by imaginative, critical thought that seeks good explanations. That is good philosophy, and good science, both of which have always existed in some measure. For instance, children have always learned language by making, criticizing, and testing conjectures about the connection between words and reality."
"Bad philosophy has always existed too. For instance, children have always been told, "Because I say so." Although that is not always intended as a philosophical position, it is worth analyzing it as one, for in four simple words it contains remarkably many themes of false and bad philosophy. First, it is a perfect example of a bad explanation: it could be used to 'explain' anything. Second, one way it achieves that status is by addressing only the form of the question and not the substance: it is about who said something, not what they said. That is the opposite of truth-seeking. Third, it reinterprets a request for true explanation (why should something-or-other be as it is?) as a request for justification (what entitles you to assert that it is so?)... Fourth, it confuses the nonexistent authority for ideas with human authority (power) – a much-travelled path in bad political philosophy. And fifth, it claims by this means to stand outside the jurisdiction of normal criticism."
"One currently influential philosophical movement goes under various names such as postmodernism, deconstructionism and structuralism depending on historical details that are unimportant here. It claims that because all ideas, including scientific theories, are conjectural and impossible to justify, they are essentially arbitrary: they are no more than stories, known in this context as 'narratives'. Mixing extreme cultural relativism with other forms of anti-realism, it regards objective truth and falsity, as well as reality and knowledge of reality, as mere conventional forms of words that stand for an idea's being endorsed by a designated group of people such as an elite or consensus, or by a fashion or other arbitrary authority."
"Elegance is a heuristic guide to truth." There is a "need to create objective knowledge to allow different people to communicate."