The most interesting, and the most useful, fictions, are, perhaps, such, as delineating the progress, and tracing the consequences, of one strong, indulged, passions, or prejudice, afford materials, by which the philosopher may calculate the powers of the human mind, and learn the springs which set it in motion – “Understanding, and talents,” says Helvetius, “being nothing more, in men, than the produce of their desires, and particular situations.” Of the passion of terror Mrs. Radcliffe has made admirable  use in her ingenious romances. – In the novel of Caleb Williams, curiosity in the hero, and the love of reputation in the soul-moving character of Falkland, fostered into ruling passions, are drawn with a masterly hand.
For the subject of these Memoirs, a more universal sentiment is chosen – a sentiment hackneyed in this species of composition consequently more difficult to treat with any degree of originality; – yet, to accomplish this, has been the aim of the author; with what success, the public will, probably, determine.
Every writer who advances principles, whether true or false, that have a tendency to set the mind in motion, does good. Innumerable mistakes  have been made, both moral and philosophical: – while covered with a sacred and mysterious veil, how are they to be detected? From various combinations and multiplied experiments, truth, only, can result. Free thinking, and free speaking, are the virtue and characteristics of a rational being: -- there can be no argument which militates against them in one instance, but what equally militates against them in all; every principle must be doubted, before it will be examined and proved.
It has commonly been the business of fiction to pourtray characters, not as they really exist, but, as, we are told, they ought to be – a sort of ideal perfection, in which nature and passion are melted away, and jarring attributes wonderfully combined. 
In delineating the character of Emma Courtney, I had not in view these fantastic models: I meant to represent her, as a human being, loving virtue while enslaved by passion, liable to the mistakes and weaknesses of our fragile nature. – Let those readers, who feel inclined to judge with severity the extravagance and eccentricity of her conduct, look into their own hearts; and should they there find no record, traced by an accusing spirit, to soften the asperity of their censures – yet, let them bear in mind, that the errors of my heroine were the offspring of sensibility; and that the result of her hazardous experiment is calculated to operate as a warning, rather than as an example. – The philosopher – who is not ignorant, that light and shade are more powerfully contrasted in minds rising above  the common level; that, as rank weeds take strong root in a fertile soil, vigorous powers not unfrequently produce fatal mistakes and pernicious exertions; that character is the produce of a lively and constant affection – may, possibly, discover in these Memoirs traces of reflection, and of some attention to the phaenomena of the human mind.
Whether the incidents, or the characters, are copied from life, is of little importance – The only question is, if the circumstances, and situations, are altogether improbable? If not – whether the consequences might not have followed from the circumstances? – This is a grand question, applicable to all the purposes of education, morals, and legislation – and on this I rest my moral – “Do men gather figs of thorns,  or grapes of thistles?” asked a moralist and a reformer.
Every possible incident, in works of this nature, might, perhaps, be rendered probable, were a sufficient regard paid to the more minute, delicate, and connecting links of the chain. Under this impression, I chose, as the least arduous, a simple story – and, even in that, the fear of repetition, of prolixity, added, it may be, to a portion of indolence, made me, in some parts, neglectful of this rule; – yet, in tracing the character of my heroine from her birth, I had it in view. For the conduct of my hero, I consider myself less responsible – it was not hismemoirs that I professed to write.
I am not sanguine respecting the success of this little publication. It is  truly observed, by the writer of a late popular novel* -- “that an author, whether good or bad, or between both, is an animal whom every body is privileged to attack; for, though all are not able to write books, all conceive themselves able to judge them. A bad composition carries with it its own punishment – contempt and ridicule; – a good one excites envy, and (frequently) entails upon its author a thousand mortifications.”
To the feeling and the thinking few, this production of an active mind, in a season of impression, rather than of leisure, is presented.
* The Monk. [Hays's note.]