In Chapter 7 Frances Wright has Epicurus say this:
QuoteZeno, in his present speech, has rested much of the truth of his system on its expediency; I, therefore, shall do the same by mine. The door to my gardens is ever open, and my books are in the hands of the public; to enter, therefore, here, into the detail or the expounding of the principles of my philosophy, were equally out of place and out of season. ‘Tell us not that that is right which admits of evil construction; that that is virtue which leaves an open gate to vice.’
In a generic sense Wright could have picked up this idea for her argument from any number of places in Cicero or Plutarch. As we are currently as of this writing dealing with Tusculan Disputations, Part 3, Section XX, it seems to me that some of the text here is particularly apt to have generated the need to frame the argument the way Wright did.
This section specifically comes to mind, with Cicero speaking against Epicurus:
QuoteThe last mistake he falls into in common with some others; which is this: that as virtue is the most desirable thing, and as philosophy has been investigated with a view to the attainment of it, he has separated the chief good from virtue. But he commends virtue, and that frequently; and indeed C. Gracchus, when he had made the largest distributions of the public money, and had exhausted the treasury, nevertheless spoke much of defending the treasury. What signifies what men say, when we see what they do? That Piso, who was surnamed Frugal, had always harangued against the law that was proposed for distributing the corn, but when it had passed, though a man of consular dignity, he came to receive the corn. Gracchus observed Piso standing in the court, and asked him, in the hearing of the people, how it was consistent for him to take corn by a law he had himself opposed? “It was,” said he, “against your distributing my goods to every man as you thought proper; but, as you do so, I claim my share.” Did not this grave and wise man sufficiently show that the public revenue was dissipated by the Sempronian law? Read Gracchus's speeches, and you will pronounce him the advocate of the treasury. Epicurus denies that any one can live pleasantly who does not lead a life of virtue; he denies that fortune has any power over a wise man: he prefers a spare diet to great plenty, and maintains that a wise man is always happy. All these things become a philosopher to say, but they are not consistent with pleasure. But the reply is, that he doth not mean that pleasure: let him mean any pleasure, it must be such a one as makes no part of virtue. But suppose we are mistaken as to his pleasure, are we so too as to his pain? I maintain therefore the impropriety of language which that man uses when talking of virtue, who would measure every great evil by pain.