There's always a decision to make about which aspects of the cosmogonical question to take seriously and which to foreclose. 


The most ambitious decision is to not only establish first principles, but to take a further step and make claims about "why" the first principles are what they are.  This further step goes beyond the limits of reason into revelation - a divine act that can only be known through mystical union. 


Way on the other end of the spectrum, we have variants of the view that we should not allow ourselves to establish first principles at all.  Thought begins in media res  , and first principles must be either renounced altogether or subjected in principle to revision  


There are strong reasons, both epistemological and ethical, to choose one of these latter routes - but it is nevertheless hard to do so without the suspicion that the task is simply impossible.   The principles always get snuck back in through the back door


The best route is surly a combination of these two approaches - it is doubly honest.  Honest in the Hegelian/paranoiac sense of refusing to lay down first principles that are not completely certain, but also honest about the fact that this radical approach obfuscates an aspect of though that can be denied but not escaped:  there is a cosmogonical question beckoning us whether we want it to or not