Umm... Judgement based upon the accreted precedents of the previous decisions I've had to make, and the stories that have influenced my priorities in life?

How do you make decisions about anything?

Also, I'm really not sure what you mean by the term 'post-modernist', I'm far from convinced that anybody knows what that term really means. It seems to get thrown around so liberally that it has watered the currency of expression.