Lady Macbeth resembles her husband in a number of ways: she honourably and efficiently carries out her duties as a member of the aristocracy; she has powerful ambitions; she loves her spouse and is ambitious at least as much for him as for herself; finally, she also has a strong conscience. The main difference between Lady Macbeth and Macbeth lies in Lady Macbeth's utter refusal to listen to her conscience at the beginning of the play. Actually, we never actually see a conflict in Lady Macbeth between the good and evil parts of her as we do see in Macbeth. We infer her conscience from the strength of her invocation to the "spirits/ That tend on mortal thoughts." She needs so strong and so horrifying an invocation in order to repress an active conscience. Knowing that her conscience would pain her for planning and committing a murder, she calls on the spirits to "Stop up the access and passage to remorse," to "take my milk for gall," and not to permit heaven (another way of referring to her conscience) "To cry, 'Hold, hold!'" Perhaps Lady Macbeth finds it somewhat easier to ignore her conscience than her husband can ignore his because her imagination is less vivid than his. When he thinks of murdering Duncan, the picture of his doing so appears before his eyes blotting out his real surroundings. Macbeth also sees daggers pointing him to the murder and hears voices which cry, "Macbeth does murder sleep." Lady Macbeth does not have the problem of contending with this kind of imagination.
There is another difference between Lady Macbeth and Macbeth: it is in their attitude toward each other. Macbeth never in the play thinks of manipulating his wife. Later in the play, in order to save her from the torments of her conscience, he does not tell her of his plans for murder , but that is different from handling someone in such a way as to induce him to do something he may not want to do. But Lady Macbeth does manipulate her husband. This is not to say that she does not love him; on the contrary, her care for him and her tenderness toward him show that she does. She believes that her manipulating him into the murder of Duncan will attain for him the crown, which will eventually make him happier than his conscience will allow him to know that he will be. She therefore decides that she will "chastise [him] with the valour of [her] tongue." When the time comes for the fatal decision, she plays upon his manhood and his love for her. Lady Macbeth is going to get her husband what he really wants, whether or not he knows he wants it. Love, such as Lady Macbeth's which induces its object to try for more than its object wholly wants, is, we must conclude, influenced by egotism.
Now, when Lady Macbeth made the gigantic effort to repress her conscience, she apparently felt a necessity to do so only for the period in which the murder was to be committed. She never talks of needing the repression later. It appears as though she felt that once the murder was committed and "sovereign sway and masterdom" was attained, her guilt would be assuaged. Or, perhaps she felt that her conscience, once repressed by this great effort, would stay repressed. At any rate she counted neither on an irrepressible conscience nor on the consequences brought about by a kingship attained through violence, which consequences only brought on further acts of violence, which in turn only strengthened the conscience. The energy Lady Macbeth required to push down her conscience in the first place was great. She would need an ever-increasing energy to repress it, especially when it was always increasing in strength. Expecting only "sovereign sway and masterdom" without increased activity of her conscience, having consumed a tremendous amount of energy in first repressing her conscience, Lady Macbeth finally succumbs to its torments and can escape from them only in madness and suicide.
Her conscience victorious.
The line of her deterioration can be traced in the play. In the first place she is not altogether successful in pushing down her conscience even for the period of the murder. She would herself have murdered Duncan "had he not resembled / My father as he slept," a resemblance probably made vivid by her conscience. After the murder, when Macbeth is making excuses for having murdered outright Duncan's attendants, Lady Macbeth faints. This may be a clever ruse on Lady Macbeth's part to take attention away from Macbeth, who seems to be talking too much. It may also be relief from the nervous tension engendered by her great efforts of the last few hours. However, these are just foreshadowings of what is in store for her. The next time we see her alone, she voices her sense of insecurity, "'Tis safer to be that which we destroy, / Than by destruction dwell in doubtful joy." And later in that same scene Macbeth speaks of these terrible dreams "That shake us nightly." The us refers to him and Lady Macbeth. However, she still retains enough energy to attempt to keep Macbeth from revealing his fears in the banquet scene. Yet, once the guests have left in disorder, she is listless, all energy gone. She can speak only in single sentences; Macbeth is dominant; he makes all the decisions, she none. When next we see her, her conscience has emerged victorious. Despite "the dignity of the whole body," which she apparently can maintain during the day and perhaps even in sleepwalking, at night her conscience rips her with fears and shattered memories of crimes. Worst of all, the stain and smell of Duncan's blood seems to cling to her hands. When we finally hear of her, it is thought that she has committed suicide. Almost certainly she has. We had heard earlier of her escape into madness, which was probably no escape, for undoubtedly the memories remained; and now suicide has become a final escape. Suicide was the only way in which she could control the conscience she so thoughtlessly and resolutely believed she could repress.