We are commonly taught by experience, that all well-doing requireth gratitude. And even though the benefactor doth not covet it for himself, yet he should desire it, that the recipient may not suffer dishonour where the giver hath acquired virtuous merit. And such a special communion is there between these two acts, to wit, giving and thanking, that the first requireth the second by way of obligation. And did not the former[A] exist, it would not be possible for there to be gratitude in the world. Wherefore, Saint Thomas,[B] who was the most clear teacher[N1] among the Doctors of Theology, saith in the second book of the second part of his work, in the 108th section, that every action returneth by nature to the cause from which it first proceeded. Therefore, since the giver is the chief cause of the benefit received by the other, it is requisite, by the ordinance of Nature, that the good he doth should come back to him in the shape of a fitting gratitude. And by this return we are enabled to understand the natural likeness between the works of Nature and those that give moral aid, for all things bring about a proper return, starting from a commencement and progressing till in the end they accomplish the recompence we speak of. And, in proof of this, Solomon saith in the book of Ecclesiastes, that the sun riseth over the earth, and, having encircled all things, returneth to where it first appeared. The rivers also proceed from the sea, and ceasing not their course, are continually returning to it. A like thing happeneth in the moral order, for all good that cometh from a generous will, doth run a straight course until it arrive at the fitting recipient, and then afterwards it returneth naturally to the place where the generosity allowed it to begin; and such a return bringeth about that sweet union between those that do good and those that receive it, of which Tully speaketh when he saith that no service is more necessary than gratitude, in order that the good may return to him who gave it. [Footnote A: _I.e._, conferring of favours.] [Footnote B: _I.e._, Aquinas. See note 1, in vol. ii. Throughout the present volume the numbers inserted in the text refer to historical and other notes which will be appended to vol. ii.]