It is clear from Laurent's first introduction in Chapter Five of this novel that he is a character unlike any other the reader has met so far, and this is certainly the case for Therese, who is seemingly entranced by this figure who comes before her so full of life and vigour. Note how she is described as watching him as he sits before her:
Laurent, who was tall and robust, with a florid complexion, astonished her. It was with a feeling akin to admiration, that she contemplated his low forehead planted with coarse black hair, his full cheeks, his red lips, his regular features of sanguineous beauty. For an instant her eyes rested on his neck, a neck that was thick and short, fat and powerful. Then she became lost in the contemplation of his great hands which he kept spread out on his knees: the fingers were square; the clenched fist must be enormous and would fell an ox.
It is particularly important to note that it is Laurent's strength, and in particular the way his strength is suggestive of violence, that attracts Therese to him. Note the final detail of his hands and how she imagines his "clenched fist" being able to "fell an ox." Laurent is the polar opposite of her husband, Camille, who has been brought up with an overbearing mother and a sickly disposition. Laurent, the son of a peasant, has been given every advantage and treats life as a prize for his taking. He is a natural go-getter and determined to seize every opportunity that life has given him, as shown by his current position and good salary. Naturalism was a literary movement that combined realism with the Theory of Evolution to argue that character was something that resulted from the environment in which one was raised. For Laurent, that has led to a disposition that is determined to do the best he can in life and to take what he wants, no matter the consequences.