The Principle of Antithesis

Darwin, Charles 1873. Expression of the Emotions in Man and Animals. London: John Murray, Albemarle Street.

When a dog approaches a strange dog or man in a savage or hostile frame of mind he walks upright and very stiffly; his head is slightly raised, or not much lowered; the tail is held erect and quite rigid; the hairs bristle, especially alon the neck and back; the pricked ears are directed forwards, and the eyes have a fiked stare [...] (Darwin 1873: 50)

At least the part about the eyes seems to apply to humans as well.

Let us now suppose that the dog suddenly discovers that the man whom he is approaching, is not a stranger, but his master; and let it be observed how completely and instantaneously his whole bearing is reversed. Instead of walking upright, the body sinks downwards or even crouches, and is thrown into flexuous movements; his tail, instead of being held stiff and upright, is lowered and wagged from side to side; his hair instantly becomes smooth; his ears are depressed and drawn backwards, but closely to the head; and his lips hang loosely. (Darwin 1873: 51)

E.g. the dog relaxes.

Not one of the above movements, so clearly expressive of affection, are of the least direct service to the animal. They are explicable, as far as I can see, solely from being in complete opposition or antithesis to the attitude and movements which, from intelligible causes, are assumed when a dog intends to fight, and which consequently are expressive of anger. (Darwin 1873: 51)

Opposition and antithesis are indeed synonymous. It is also apparent that instead of emotion Darwin is talking about attitude. The confusion around these terms remains well into the other half of the 20th century.

Let us now look at a cat in a directly opposite frame of mind, whilst feeling affectionate and caressing her master; a mark how opposite is her attitude in every respect. (Darwin 1873: 56)

But he begins not from forms of behaviour that are of an opposite nature, but from an "opposite frame of mind". How does he know to oppose frames of mind?

This contrast in the attitudes and movements of these two carnivorous animals, under the same preased and affectionate frame of mind, can be explained, as it appears to me, solely by their movements standing in complete antithesis to those which are naturally assumed, when these animals feel savage and are prepared either to fight or to seize their prey. (Darwin 1873: 57)

And yet here he states that it is the behaviours that matter and it seems that "frames of mind" can somehow be assumed.

This consisted in the head drooping much, the whole body linking a little and remaining motionless; the ears and tail falling suddenly down, but the tail was by no means wagged. With the falling of the ears and of his great chaps, the eyes became much changed in appearance, and I fancied that they looked less bright. His aspect was that of piteous, hopeless dejection; and it was, as I have said, laughable, as the cause was so slight. Every detail in his attitude was in complete opposition to his former joyful yet dignified bearing; and can be explained, as it appears to me, in no other way, except through the principle of antithesis. (Darwin 1873: 60)

Ah and here we have Darwin using an already made-up human metaphor for expressing such differences. That is, he is referring to the bright/dim or light/dark symbolism of interpreting facial expressions and looks/gazes. His antitheses are not as innocent and natural as they may appear.

The Cistercian monks thought it sinful to speak, and as they could not avoid holding some communication, they invented a gesture language, in which the principle of opposition seems to have been employed. (Darwin 1873: 61)

Sebeok compiled a book on the Monastic Sign Language. And the original source Darwin is quoting, Tylor's Early History of Mankind (1870) is available on archive.org

[...] and partly on the practice of the deaf and dumb and of savages to contract their signs as much as possible for the sake of rapidity. (Darwin 1873: 62)

Ooh, cue reduction!

With mankind the best instance of a gesture standing in direct opposition to other movements, naturally assumed under an opposite frame of mind, is that of shrugging the shoulders. This expresses impotence or an apology, - something which cannot be done, or cannot be avoided. (Darwin 1873: 62-63)

This has confused me since first reading the third edition: what is the antithesis of a shrug?

When my terrier bites my hand in play, often snarling at the same time, if he bites too hard and I say gently, gently, he goes on biting, but answers me by a few wags of the tail, which seems to say "Never mind, it is all fun." (Darwin 1873: 63)

And of course metacommunication shows up.