As I added virtue after virtue to the female monster in my mind, and the result remained still inanimate and unalluring, I realised that the lack I was conscious of was not any new perfection, but just one or two honest human imperfections.

And this, try as I would, was just what I could not imagine.
For, if you reflect a moment, you will see that, while it is easy to choose what virtues we would have our wife possess, it is all but impossible to imagine those faults we would desire in her, which I think most lovers would admit add piquancy to the loved one, that fascinating wayward imperfection which paradoxically makes her perfect.
Faults in the abstract are each and all so uninviting, not to say alarming, but, associated with certain eyes and hair and tender little gowns, it is curious how they lose their terrors; and, as with vice in the poet's image, we end by embracing what we began by dreading.

You see the fault becomes a virtue when it is hers, the treason prospers; wherefore, no doubt, the impossibility of imagining it.

What particular fault will suit a particular unknown girl is obviously as difficult to determine as in what colours she will look her best.
So, I say, I plied my brains in vain for that becoming fault.

It was the same whether I considered her beauty, her heart, or her mind.