you could ask him to explain his personal metaphysical understanding and how he came to it – a cascade of further questions will flow as he explains his metaphysical framework for his understanding of life the universe and everything.

revel in the fact that the more attentive you are the better his explanation will be

and if you ever get to feeling awestruck – hit him with a few curveballs like "what is Good" and "why does evolution take place"
References :

Thats an excellent question;
For the current philosophical,mathematicians and philosophers are likely to be aware-of,if not even use,the intricate workings of,what i call,the equatuion makers.
That this is definately no joke-and,somewhere,these things are being (philosophy/mathematically or both)-discussed,criticised,"furthered" and handed-on (= taught!),is a reality;one only has to go to the current analytical philosophical magazines to know this.
And..if my experience is anything to go by…the ordinary student may be totally "lost" when the equation-making starts,on those rather specialist pages.

All the editors of these writings have been shown/taught and know of some so-called philosophy basics; some history( Plato,aristotle ect) and of course some mathematical training/basics or complex.

So one can see that there are all sorts of assumption,"truths",ideas and beliefs that lay behind their writings-and-equations.

As i said,you have an excellent question;and i would start by having a look through a selection of the above current mags(i saw them at my university library;a search on the internet should produce something too).
And i would do this with an "open mind";to try to find-out what the assumptions are,what are the problems that they are discussing-with-a-view to a/their solution.

P.s. The above is to do with philosophy.
You should know that everyday metaphysics is done-all-the-time and has to do with doing math/art and even "crafts" too!
And no-one interested in philosophy,and its history,should ever forget the shananigans that started in philosophy last century;i mean the disgusting,taught nonsense (by the western "positivists/analysists") that metaphysics was NOT logical-and-thus-to-be-abolished from philosophy !
Popper and others successfully opposed that-serious at that time-Trash !!!
References :
For some of the history/workings of modern foundational metaphysics,read the history of the Polish philosophy school,pre-world war 2.(The author is McCall-check that spelling-and the book is called,Polish logic between the wars or,Polish philosophy between the wars(!)).
p.s. its a truely good source!