When Jack took Nell into his arms
He knew he acted ill,
And thought as he enjoyed her charms
Of his fiancée Jill.
"Poor dear," he sighed, "she dreams of me,
I shouldn't act like this;
But after all, she cannot see,
And ignorance is bliss."

Yet Jill at that same moment was
In Fred's embrace close caught,
And just a little sad because
Of sweetheart Jack she thought.
"Poor dear," she sighed, "he loves me so,
And what's a little kiss?
Or two or three - he'll never know,
And ignorance is bliss."

Now in fond wedlock all is well,
Though in their nuptial bed,
Jack's thought will sometimes stray to Nell,
And Jill's to handsome Fred.
Yet though in fancy they may flirt,
There's nothing much amiss:
What they don't know will never hurt -
Aye, Ignorance Is Bliss.

Robert William Service

http://www.poemhunter.com/poem/the-bliss-of-ignorance/