It may be easier to imagine someone trying to derive mathematics all by themselves, since it's less abstract. It's not that they won't come up with anything, it's that everything that even a genius can come up with in their lifetime will be something that the whole of humanity has long since come up with, chewed over, simplified, had a rebellion against, had a counter-rebellion against the rebellion, and ultimately packaged it up in a highly efficient manner into a textbook with cross-references to all sorts of angles on it and dozens of elaborations. You can't possible get through all this stuff all on your own.

The problem is less clear in philosophy than mathematics, but it's still there. It's really easy on your own terms to come up with some idea that the collective intelligence has already revealed to be fatally flawed in some undeniable manner, or at the very least, has very powerful arguments against it that an individual may never consider. The ideas that have survived decades, centuries, and even millenia against the collective weight of humanity assaulting them are going to have a certain character that "something someone came up with last week" will lack.

(That said I am quite heterodox in one way, which is that I'm not a big believer in reading primary sources, at least routinely. Personally I think that a lot of the primary sources noticeably lack the refinement and polish added as humanity chews it over and processes it and I prefer mostly pulling from the result of the process, and not from the one person who happened to introduce a particular idea. Such a source may be interesting for other reasons, but not in my opinion for philosophy.)

Well, sure, but mathematics is the domain for which this holds maybe the most true out of any. It's less true for fields which are not as old.

I'm not sure if this counterpoint generalizes entirely to the original critique, since certainly LessWrongers aren't usually posting about or discussing math as if they've discovered it-- usually substantially more niche topics.

... philosophy is if anything older than what we call mathematics.

I suppose you're right about that, so I can't make the argument go through by saying "mathematics" vs "philosophy". Maybe what I should say instead is that as some dialectics advance/technologies develop, subfields of both such things sprout up and have a lot of low-hanging fruit to pick, and in these cases, the new work will be descended from but not too-essentially informed by the prior work.

Like mathematical logic (in the intersection of math and philosophy) didn't have that many true predecessors and was developed very far by maybe only 5-10 individuals cumulatively, or information theory was basically established by Claude Shannon and maybe two other guys, or various aspects of convex optimization or Fourier analysis were only developed in the 80s or so, it stands to reason that the AI-related applications of various aspects of philosophy are ripe to be developed now. (By contrast, we don't see, as much, people on LW trying to redo linear algebra from the ground up, nor more "mature" aspects of philosophy.)

(If anything, I think it's more feasible than ever before, also, for a bunch of relative amateurs to non-professionally make real intellectual contributions, like noticeably moreso than 100 or even 20 years ago. That's what increasing the baseline levels of education/wealth/exposure to information was intended to achieve, on some level, isn't it?)

Not if they refuse to read all the existing information because they think they came up with it all.

Just teasing here, but I presume you’re a social conservative…? ;)

Generally conservatives only want to conserve the way the world is as they grow up. Whether that involves respect for prior ideas and thought depends on their current ideas - hence the book burning.

Odds are good that the millions of people who have also read and considered these ideas have added to what you came up with at 6. Odds are also high that people who have any interest in the topic will probably learn more by reading Descartes and Kant and the vast range of well written educational materials explaining their thoughts at every level. So if you find yourself telling people about these ideas frequently enough to have opinions on how they respond, you are doing both yourself and them a disservice by not bothering to learn how the ideas have already been criticized and extended.

It really depends on why you are having a philosophical discussion. If you are talking among friends, or just because you want to throw interesting ideas around, sure! Be free, have fun.

I come from a physics background. We used to (and still) have a ton of physicists who decide to dable in a new field, secure in their knowledge that they are smarter than the people doing it, and that anything worthwhile that has already been thought of they can just rederive ad hoc when needed (economists are the only other group that seems to have this tendency...) [1]. It turned out every time that the people who had spent decades working on, studying, discussing and debating the field in question had actually figured important shit out along the way. They might not have come with the mathematical toolbox that physicists had, and outside perspectives that challenge established thinking to prove itself again can be valuable, but when your goal is to actually understand what's happening in the real world, you can't ignore what's been done.

[1] There even is an xkcd about this:

https://xkcd.com/793/

Also http://www.smbc-comics.com/comic/2012-03-21 (I am a physicist myself)

Here's a very simple explanation as to why it's helpful from a "first principles" style analogy.

Suppose a foot race. Choose two runners of equal aptitude and finite existence. Start one at mile 1 and one at mile 100. Who do you think will get farther?

Not to mention, engaging in human community and discourse is a big part of what it means to be human. Knowledge isn't personal or isolated, we build it together. The "first principles people" understand this to the extent that they have even built their own community of like minded explorers, problem is, a big part of this bond is their choice to be willfully ignorant of large swaths of human intellectual development. Not only is this stupid, it also is a great disservice to your forebears, who worked just as hard to come to their conclusions and who have been building up the edifice of science bit by bit. It's completely antithetical to the spirit of scientific endeavor.

Did you discover it from first principles by yourself because it's a natural conclusion anyone would reach if they ponder the subject?

Or because western culture reflects this theme continuously through all the culture and media you've immersed in since you were a child?

Also the idea is definitely not new to Descartes, you can find echoes of it going back to Plato, so your idea isn't wrong per se. But I think it underrates the effect to which our philosophical preconceptions are culturally constructed.

Because it's a natural conclusion anyone would reach if they ponder the subject. Sorry, I thought I expressed that opinion clearly. I don't think I was exposed to that idea through media by that age.

How could you say that your views are aligned with those of Descartes and Kant if you have not seriously engaged with their works and what others have written about them?

All serious works in philosophy (Kant especially) are subject to interpretation. Whole research programmes exist around the works of major philosophers, interpreting and building on their works.

One cannot really do justice to e.g. the Critique of Pure Reason by discussing it based on a high level summary of the “main ideas” contained in it. These works have had a major impact on the history of Western philosophy and were groundbreaking at the time (and still are).

I think they basically agree with your point here -- they mention Descartes and Kant to say roughly "I hold basically these ideas, but I don't mention the philosophers' names when I talk about them because 1) I came to them independently, and 2) the people I'm talking to are not familiar with the context so situating our conversation there isn't helpful." Their argument is that you can have philosophical conversations without relying on the context of the canon, and that in a first-level discussion they wouldn't bring up Descartes or Kant.

Did I give you the impression from my comment that I haven't read Descartes and Kant? That's not what I intended to say.

There’s definitely a tension between having a low tolerance for crankery and being open to fresh perspectives. If I’m being charitable to the critics of Rationalism (big “r”), I suppose that they have encountered arguments from Rationalists that struck them as wrong specifically in a way that would have been avoided if the person making the argument had read any of the relevant literature.