Thank you for your incisive response. I would say that yes, it is important to "borrow structure of both discussion and thought from the past", yet we must do so carefully. We can use these structures as inspiration and models for our own inquiry. But when the ideas we read about come to preclude our own independent inquiry, it becomes harmful. Therefore, I think it is more important that philosophy passes down the flame of doubt, to inspire us to independent inquiry, rather than passing down ideas, which may drive us away from independent inquiry.

Philosophy, I think,should be less preoccupied with transmitting 'knowledge' (whatever that is), and more concerned with transmitting the desire for knowledge.

I like Karl Jasper's idea a lot - that each individual must conduct his own independent enquiry into truth, and that others cannot show him the destination, but only act as 'signposts', revealing different routes he can explore. In this line of thinking, ideas are not so much about forming a "foundation" as about inspiring new approaches to old questions.

I hope I have at least somewhat addressed your question?