Hey Philhosophy
another philosopher here using GPT3 for philosophy as well
Isn’t it awesome to finally have a patient, unemotional interlocutor to test philosophical theses till your wife yells at you? lol ;p this is the best tool humans have ever made
to answer your questions
yes it is stochastic - but this is not really the issue - this will give very minor fluctuations when you are on the cusp of entity semantic relation (like say between x.1% and x.2 percent off for hypothetical example, the quantum bits might choose one or the other)
yes fine tuning would help, theoretically -but really not because on a prompt like this you want to not polute the semantic relations - you want it’s true opinion so to speak, if you keep using dog examples then no arguments about dogs, even mamals or cats will ever be safe again (eg) - it will all influenced by your arbitrary examples, make sure to randomly choose different points of the argument, never accidentally comparing 1 and 3 too much for example
in this case, keeping it simple for it, and saying “please” literally, accidentally, tied into a semantic of deeper grammar and more well reasoned, explicative, responses. I have seen how changing one, seemingly insignificant word, can change an entire branch of hidden semantics (in ethics, from the right action suddenly being the good action, or vice versa… a large distinction lost on GPT3, for example)
the short answer is keep it simple and just say please (and i use davinci not instruct - i don’t see it being any better, not for philosophy - i’ve spent thousand hours at this… literally)
for a prompt like this where you don’t want to taint the answer with your prompt, you need to keep the examples light - DON’T have those big C1W2E4.Wittgenstein format, you are confusing it 
also this does not appear to be syllogistic, GPT3 can and does and will think syllogistically out of the box, so that will mess with your random analyses as well between propositions - GPT3 is looking for structure, if you don’t want that structure, don’t give it any 
so keep it simple, less words is better, and give it a very good thorough example - just one really good one should do for what oyu want to to - keep temperature at zero of course - use the QnA settings from their example, that should be best for you, learn to use the probabilities feature to see what ir wanted to say and give it examples to move the numbers up as you want (you cannot move the numbers down, only up, give it positive reinforcement, no negatives)
if you have any questions at all feel free to msg me! i’d be happy to help