There are several reasons for why Melville gives the lawyer so much difficulty in knowing how to handle Bartleby, including not knowing how to fire him in "Bartleby the Scrivener, A Tale of Wall Street." The reason have to do with the personal qualities Melville is exploring and themes he is presenting. First, in the lawyer's character, Melville is exploring the personality traits of contentment coupled with successful enterprise that is respected and rewarded even though it is without energetic ambition. In Bartleby he is exploring a personality that is trapped by a selfish capitalist society that hasn't been modified by charitable and equitable instincts that work to level the great divide between the wealthy and the laborer.
Second, the themes Melville is concerned with are related to self-expression and self-fulfillment. One of the themes is the experience of being at a dead end in life and wall off from happiness and realization of one's self. Another is the ambiguity of motives in an individual's existence. For instance, we never really understand Bartleby's motives for staring at the wall outside. A third relevant theme is dominance versus freedom. From the lawyers description of himself, his employees, his work philosophy, it is clear that the lawyer values and respects personal freedom, even as it is expressed by Turkey, Nippers, and Ginger Nut. Firing Bartleby would require the lawyer to disregard Bartleby's freedom and dominate him as well as to undermine his own freedom to have a care free work life as he desires.