Ordinary language is all right.
One could divide humanity into two classes:
those who master a metaphor, and those who hold by a formula.
Those with a bent for both are too few, they do not comprise a class.
(A special problem, coincidental thematics.)
There is a 'we' spoken in agreement, a 'we' used in seeking agreement, a 'we' used to define with whom and in what agreement shall consist. And there is a use of 'we' to declare that one is with someone else: what Goffman calls being part of 'a with'. But how do (and can) two people alone together say 'we'? (And how is that like, or unlike, a solitary's use of 'I'? Or saying 'I' to oneself? Why do they say 'we' and not just 'you' and 'I'? Do they?)
A counterpart for 5.62's 'language which alone I understand': 'that language which we alone understand'.
'… to speak about the will in so far as it is the subject of ethical attributes': so, to really communicate the purest joys, the most personal sufferings (the most personal dimension of them), in their heights or depths?