The facts about friendship (objections a-d) used to support the view that the circumstances of justice are displaced by the circumstances of friendship (the Inverse Proportionality thesis) are, in Aquinas's own understanding of friendship, either not true —(a), (b), (d)—or (in my own view) irrelevant to the Inverse Proportionality thesis—(c).
Aquinas's theological view that there is no merit without (or “outside”) charity can also be expressed non-theologically: when two persons are separated by a wide gap, the actions of the inferior do not lay just claims on the superior unless the inferior is a friend. The inferior's actions become effective in entitling him to just deserts only when proportional equivalence between the superior's and the inferior's actions becomes possible. Proportional equivalence obtains only when the inferior's actions are seen as the common actions of both friends. An action is common to two persons when neither of the persons is merely a part or tool of the other, both cooperate freely, and both share reasons. Friends' actions are common actions.
It must be stressed that this reading of Aquinas's view does not lend support to the notion that friendship takes precedence over justice (“you only have justice if you have friendship first”). In this reading, Aquinas believes that, in the transition from a superiorinferior relationship to a relationship between partners, friendship and the possibility of just interaction arise concomitantly.