My friend states that 'morality is subjective' since one can construct definitions based on arbitrary intensions and extensions of a well-defined set viz. 'My own morally not bad actions' from the universal set 'U=set of acts that can be done by humans'.
My doubt: I feel that 'morality is subjective' is again a moral position, is it an objective view? How can we say that the set 'U=set of acts that can be done by humans' is well-defined? Especially the term 'acts'.
If one can tweak definitions, particularly using set-theoretic approaches to morality, then, how does one deal with the conflicts that arise from this conflicts such as trying to include 'Believe in god' as an action in this well-defined set U? It seems that crafting some sort of categorical imperative is problematic.
Is it even possible to define a set U of acts done by humans is moral and then discriminate which activities are in and out of the set?