Alius est amor concupiscentiae, et alius est amor amicitiae, quia ad illud bonum quod quis vult alteri, habetur amor concupiscentiae, ad illud autem cui aliquis vult bonum, habetur amor amicitiae.
Love of concupiscence is distinct from love of friendship because man has love of concupiscence towards the good that he wishes to another, and love of friendship towards him to whom he wishes good.
Amor non dividitur per amicitiam et concupiscentiam, sed per amorem amicitiae et concupiscentiae. Nam ille proprie dicitur amicus, cui aliquod bonum volumus, illud autem dicimur concupiscere, quod volumus nobis.
Love is not divided into friendship and concupiscence, but into love of friendship, and love of concupiscence. For a friend is, properly speaking, one to whom we wish good, while we are said to desire, what we wish for ourselves.
Haec autem divisio est secundum prius et posterius. Nam id quod amatur amore amicitiae, simpliciter et per se amatur, quod autem amatur amore concupiscentiae, non simpliciter et secundum se amatur, sed amatur alteri. Sicut enim ens simpliciter est quod habet esse, ens autem secundum quid quod est in alio; ita bonum, quod convertitur cum ente, simpliciter quidem est quod ipsum habet bonitatem; quod autem est bonum alterius, est bonum secundum quid. Et per consequens amor quo amatur aliquid ut ei sit bonum, est amor simpliciter, amor autem quo amatur aliquid ut sit bonum alterius, est amor secundum quid.
Now the members of this division are related as primary and secondary: since that which is loved with the love of friendship is loved simply and for itself; whereas that which is loved with the love of concupiscence, is loved, not simply and for itself, but for something else. For just as that which has existence, is a being simply, while that which exists in another is a relative being; so, because good is convertible with being, the good, which itself has goodness, is good simply; but that which is another's good, is a relative good. Consequently the love with which a thing is loved, that it may have some good, is love simply; while the love, with which a thing is loved, that it may be another's good, is relative love.
In amicitia utilis et delectabilis, vult quidem aliquis aliquod bonum amico, et quantum ad hoc salvatur ibi ratio amicitiae. Sed quia illud bonum refert ulterius ad suam delectationem vel utilitatem, inde est quod amicitia utilis et delectabilis, inquantum trahitur ad amorem concupiscentiae, deficit a ratione verae amicitiae.
When friendship is based on usefulness or pleasure, a man does indeed wish his friend some good, and in this respect the formal aspect of friendship is preserved. But since he refers this good further to his own pleasure or use, the result is that friendship of the useful or pleasant, insofar as it is connected with love of concupiscence, loses the formal aspect of true friendship.