Phase the First, or the first part of the book, is called The Maiden because that is precisely what Tess is. She is a virgin. In chapter XI, however, she gets lost in the woods with Alec D’Urberville. She is wearing only a light summer dress because she didn't think she'd be out that late. Alec gives her his coat and goes goes off to try to get his bearings. When he comes back to her, Tess is asleep. It is then that Alec takes advantage of her. We know that because the next section is titled "Maiden No More."

Phase the First, the Maiden, is so-called because it is the time of life when young women first enter the complex world of sexuality, with its temptations to both acquiesce to the relentless advances of men yet remain chaste as society demands. Tess is among the young women facing these challenges, but her incredible beauty sets her distinctly apart. She is unprepared for the vicious world of adulthood.

The narrator describes this season of being a maiden as having one foot in childhood and one foot in womanliness. Like a young flower about to turn from bud to bloom,

Tess Durbeyfield at this time of her life was a mere vessel of emotion untinctured by experience...The pouted-up, deep red mouth....had hardly as yet settled into its definite shape...

Phases of her childhood lurked in her aspect still. As she walked long to-day, for all her bouncing, handsome womanliness, you could sometimes she her twelfth year in her cheeks or her ninth sparkling from her eyes...

....A small minority, mainly strangers, would look long at her in casually passing by, and grow momentarily fascinated by her freshness, and wonder if they would ever see her again...

Tess, a country girl, will be no match in cunning or in maturity. Alec will soon see that her phase of maidenhood will pass almost as quickly as it had begun.