What kind of language features appear in Lady Macbeth's line "too full o' the milk of human kindness"?

Question

In Macbeth Act I Scene 5, Lady Macbeth says the following:

Glamis thou art, and Cawdor; and shalt be
What thou art promised: yet do I fear thy nature;
It is too full o' the milk of human kindness
To catch the nearest way: thou wouldst be great;

What kind of language features can be found in the line:

too full o’ the milk of human kindness

Also, what does it mean about how she views Macbeth’s ability to grasp after power and status?

Answer 1

In addition to the devices mentioned in the other answers, the phrase "milk of human kindness" also deploys two other devices:

1. Paronomasia, or more simply, a pun. Kindness typically means gentleness, generosity, and/or helpfulness, which is the most readily accessible sense here. But kind can also mean category, as in:

   What kind of books do you like to read?

   So when Lady Macbeth says human kindness, one sense of the term is that Macbeth is too much of a human being, too firmly in the category of humanness, to just pursue his own interests at all costs (catch the nearest way) the way a wild animal might. Tsundoku's answer touches upon this sense, but does not explicitly mention the punning nature of this phrase, hence this follow-up.¹

   Merriam-Webster also mentions that the word humankind has been used in the sense of all human beings or humanity in general since 1560, i.e., it was current when Macbeth was first performed around 1606. This adds to the pun. Macbeth's imbibing his mother's milk has made him a member of the human race, which has made him too categorically human, too humane, too kind, too much a member of humankind, to be the cold-blooded murderer Lady Macbeth would like him to be.

   We think of puns as low humor, and Samuel Johnson criticized Shakespeare for using them so liberally:

   A quibble was to him the fatal Cleopatra for which he lost the world, and was content to lose it.     (Preface to Shakespeare)

   But Johnson gets hold of the wrong end of the stick and proceeds to beat Shakespeare with it. In Shakespeare's hands, such quibbles (i.e., puns) are not just facile wordplay. They bring together a complex set of meanings that provide unexpected insights into character and situation. The polysemy adds to the intensity and dramatic force of Shakespeare's language and here as elsewhere, contribute tremendously to the texture of his plays. The fact that four paragraphs and a footnote can be devoted to this single pun itself attests to that.  

2. The use of a motif, a recurrent image that takes on symbolic meaning. Babies and milk are a motif in Macbeth. North Læraðr's answer mentions how Lady Macbeth has invited spirits to take her milk for gall. Elsewhere, she tells Macbeth that she would kill her own suckling child:

             I have given suck, and know
   How tender ’tis to love the babe that milks me.
   I would, while it was smiling in my face,
   Have plucked my nipple from his boneless gums
   And dashed the brains out ...     (I.vii.62–66)

   Still later in the play, Malcolm tests Macduff's sincerity by claiming he is temperamentally unsuitable to be king. The image Malcolm uses for bad governance again that of milk:

   Nay, had I power, I should
   Pour the sweet milk of concord into hell,
   Uproar the universal peace, confound
   All unity on earth.     (IV.iii.113–116)

   This replicates the idea that even milk and breastfeeding are untrustworthy in the unnatural world of Macbeth. Having or giving milk are not good things, and can be put to unkind purposes. The images of babies throughout Macbeth are beyond the scope of this answer (and perhaps would make for a good question on this site), but they intersect with the images of milk to deepen this motif.

It is worth noting that both these devices, paronomasia and motif, are akin to each other: they act by layering meanings. In the first, the mechanism is verbal. Many disparate senses of human kindness work together to build a complex network of meaning. In the second, the mechanism is that of the image. Through strategic repetition, the image accretes a cluster of meanings and associations. The phrase the milk of human kindness brings both these devices together in a highly compressed way, in a remarkable example of Shakespeare's rhetorical dexterity.

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Note

     ¹ Shakespeare famously uses this exact same pun on kind (gentle, category) in Hamlet's very first words onstage:

A little more than kin and less than kind. (I.ii.67)

Claudius is doubly related to Hamlet, being his uncle as well as his stepfather, so he is more than kin. But of course Claudius is less than kind, both because he is a ruthless murderer and because he's not the same kind of man as Hamlet's father. Hamlet's line could also be taken to refer to himself. He is more than kin to Claudius, being both nephew and stepson. But since he is not actually Claudius's son, he is less than kind as in the German sense of kind: child. The contemporary pronunciation of kind would also make the pun clearer. See ivanhoescott's question on ELU, including Peter Shor's comment and Mick's answer.

Answer 2

1. The rhythm has a double iamb (it is too full), an anapest (o’ the milk), and a ‘feminine’ ending (kindness):

   x  x     /   /     x    x  /     x   /     x   /       x
   It is | too full | o' the milk | of hu- | man kind- | ness
   

2. ‘Milk’ is a metaphor.

3. The line as a whole is ironic: Macbeth has only just enough kindness to balk at outright murder, and Lady Macbeth knows it.

   We are somewhat surprised to hear from her that Macbeth is “too full o’ the milk of human kindness to catch the nearest way”, because in the whole drama we find no trace of this milk of human kindness. We have to assume that the lady still has an over-high opinion of her husband, which, however, she will shortly lose. We already know him as a ruthlessly determined “murderer in thought” and as a perfect hypocrite: this nature of his is not contradicted by the letter; it is only somewhat veiled in it. The lady knows immediately what he wants; she also knows and openly confesses that his “milk of human kindness” will not deter him from attempting the death of old King Duncan, but only from “catching the nearest way”, that is, doing the deed with his own hand.

   _{Friedrich Bodenstedt (1873). William Shakespeare’s dramatische Werke: Macbeth, p. vi. Leipzig: F. A. Brodhaus.}

Answer 3

Regarding your first question, it contains a multitude of different literary devices, but the closest to the "milk of human kindness" is I think a reification. It's defined as a

"Complex idea for when you treat something immaterial — like happiness, fear, or evil — as a material thing." [Vocabulary.com]

In this case, the "human kindness" is being objectified into milk. So we're also dealing with a symbol here now. So we ask ourselves, what is milk? Milk represents food for an infant, something nourishing and gentle. This is further explored when several lines later in the "Come Ye Spirits" soliloquy Lady Macbeth asks to

Come to my woman’s breasts,
And take my milk for gall

here, invoking milk to relate to womanhood and motherhood to something hardened and undesirable like gall (which is another word for bile). The last literary device is probably a metaphor. It's comparing Macbeth's nature (or personality) to be filled with the milk of human kindness.

All in all, Lady Macbeth does not believe that her husband is strong enough to "do whatever it takes" to become king, and she believes she has to be the ruthless force that drives Macbeth.

Answer 4

Lady Macbeth fears that her husband has too much humanity in the sense of "compassion characteristic of humane persons" (Macbeth, edited by A. R. Braunmuller, 1997). Braunmuller points out that the First Folio had "humane" instead of "human" and that

'humane' (= gentle, compassionate) was not distinguished orthographically from 'human' before 1700 (...), 'kindness' principally means 'kinship', but also connotes 'category' ('kind' = classification, group) and 'naturalness' ('kind' = nature).

Macbeth drank in this milk from his mother and it binds him "to the social order of Man" (Macbeth, edited by G. K. Hunter, 1967).

The association between milk and some type of weakness can also be found elsewhere in Shakespeare. In King Lear, Act 1, scene 4, Gonerill says to her husband, the Duke of Albany:

No, no, my lord,
This milky gentleness and course of yours (...)

And in Act 4, scene 2, she calls Albany

Milk-livered man!

In Gonerill's eyes, Albany lacks blood in his liver; instead, his liver contains too much milk.

And in Timon of Athens, Act III, scene 1, where Flaminius asks,

Has friendship such a faint and milky heart
It turns in less than two nights?

Here, milky can be understood as "weak, timorous" (Timon of Athens, edited by G. R. Hibbard, 1970).

Lady Macbeth uses the word "milk" figuratively; she thinks her husband is too "humane" (in more than one sense) or possibly to weak (i.e. insufficiently courageous or determined) to take the shortest route ("nearest way") to what has been promised to him, i.e. kingship.