William Congreve 
The Double-Dealer, a comedy [EPUB ebook] 

Sir, —I heartily wish this play were as perfect as I intended it, that it might be more worthy your acceptance, and that my dedication of it to you might be more becoming that honour and esteem which I, with everybody who is so fortunate as to know you, have for you. It had your countenance when yet unknown; and now it is made public, it wants your protection.
I would not have anybody imagine that I think this play without its faults, for I am conscious of several. I confess I designed (whatever vanity or ambition occasioned that design) to have written a true and regular comedy, but I found it an undertaking which put me in mind of Sudet multum, frustraque laboret ausus idem. And now, to make amends for the vanity of such a design, I do confess both the attempt and the imperfect performance. Yet I must take the boldness to say I have not miscarried in the whole, for the mechanical part of it is regular. That I may say with as little vanity as a builder may say he has built a house according to the model laid down before him, or a gardener that he has set his flowers in a knot of such or such a figure. I designed the moral first, and to that moral I invented the fable, and do not know that I have borrowed one hint of it anywhere. I made the plot as strong as I could because it was single, and I made it single because I would avoid confusion, and was resolved to preserve the three unities of the drama. Sir, this discourse is very impertinent to you, whose judgment much better can discern the faults than I can excuse them; and whose good nature, like that of a lover, will find out those hidden beauties (if there are any such) which it would be great immodesty for me to discover. I think I don’t speak improperly when I call you a lover of poetry; for it is very well known she has been a very kind mistress to you: she has not denied you the last favour, and she has been fruitful to you in a most beautiful issue. If I break off abruptly here, I hope everybody will understand that it is to avoid a commendation which, as it is your due, would be most easy for me to pay, and too troublesome for you to receive.