why do you think Dickens writes about Pip’s visions first of Estella and then of Miss Havisham in the old brewery?

One of the themes of this story is the relationship between good and evil. It can be argued that the convict, although a criminal, does have some good qualities. Keeping this idea in mind, why do you think Dickens writes about Pip’s visions first of Estella and then of Miss Havisham in the old brewery?