My answer, for those so bored and disengaged with the real world, was as follows:
Philosophy is the act, or result of, staving off the idea that there is nothing objective to know, no objective truth to strive for.
This was not, i should hasten to add, a post modernist rant as to the necessity for the removal of frame work etc etc. Nothing instills a more suffocating structure and framework to thought than the premise that one should remove structure or framework.
My point was essentially this. While everything we perceive in the world is human construction, where knowledge and truth is relative to where you are situated in said world, philosophy is still useful even, dare i say, crucial. The reason for this is, by doing philosophy as well as science, art, architecture etc etc, we will add to the growing collection of human 'stuff'. While it might not be objective knowledge, it's certainly information and it deals with how we interact with the world and, in so doing, we might work out why the idea that there is no ultimate knowledge to strive for is such a terrifying idea.
I also answered some potential critics. People like Bertrand Russell thought that there were things in the world that one could objectively know to be true, irrespective of humans and the empirical world. Such examples were of course 2+2=4, and his defence of induction which was, roughly: All observed A's have been B's, no observed A's have been non B's, the next A will most likely be a B, so its reasonable to conclude that all A's are B's. These statements were a priori (knowable without reference to the external world) but also analytic (ie. the truth of the statement was contained within the statement itself).
I argued that Russell was wrong here. While 2+2=4 and his logical defence of induction is indeed a priori, meaning i can sit in bed and analyse whether it is sound, it is not analytic. It is, rather, synthetic, meaning that the truth condition is not contained within the phrase but does, actually, lie outside it. So while i can see that 2+2=4 makes sense by sitting in bed, it would make no sense at all if i did not have the empirical world as background, ensuring that something and something making something else was a familiar idea. By the same token his defence of induction requires me to understand the concept that X can be Y. To know that a tree is different to a human i need firm ideas of what these two concepts entail.
This, in a roundabout way, was how i defended that idea that there is no objective truth. No mater the phrase, there will always be some form of projection onto the empirical world. I can sit inside my bubble and see that it makes sense, but i cannot sit inside my bubble and understand it, without first looking outside.
That was, by and large, it. As with all these things, it seemed quite good at the time of writing, but now i feel i have written something roughly equivalent to something released by Megadeth circa 99.
In any case, there is no Knowledge, but that shouldn't stop us thinking about stuff. The more ways we have of interacting with the world, the better, i suspect, for everyone.
Here is Sadus doing what they do: