Duncan's last words...Act I, scene VI, and VII

In scene 6, we see one of the few daylight scenes in the play. Duncan (ironically) expresses how fair the day is and how much he likes the look of the castle and its surroundings. He also calls Lady Macbeth an honoured hostess. The audience sees the irony of thses things, because we know that the Macbeths are plotting a foul murder and that Duncan has really arrived at the place of his death.

In scene 7, we see Macbeth's first true soliloquy as he talks himself out of the murder of Duncan. He lists several reasons, including the fact that he is worried he may eventually suffer the same fate as Duncan, as murder only causes more murder. He admits though that he is driven by ambition, and that this is his tragic flaw. He decides not to kill Duncan, however, because Duncan is his kingsman. Other reasons include that he is the host, and the host should protect their guests from murder, and finally, that it seems Duncan has been a good king, so he doesn't deserve to die. In the end, though, Lady Macbeth convinces him to do the deed anyway, stating that she would do anything for him if she had promised him something--even if it meant killing her own child (how gruesome). We see that Macbeth does have a conscience, but that Lady Macbeth reminds him of his ambition, and he decides to go ahead with her plan, which involves drugging the chamberlains, and then blaming the murder on them.

In this scene, we must decide whether we feel Macbeth has made these decisions and that what occurs is of his own choosing, or, do we on the other hand, feel that Lady Macbeth is responsible for the bloodshed that occurs? Or, perhaps still is the idea that the witches are responsible, although they have not appeared for several scenes.