Bloody Mary vowed never to be back from her looking glass; Alice journeyed the checkerboard in a mirror world. Buddhist philosophers advise on ‘mirrors of minds’; terming language a mirror to the mind might turn out a little relativist, however.
Cave dwellers didn’t have mirrors. They never saw their faces except in pools of water, in which many might look similar. The particular features in seeing oneself became more prominent to the human of the Antiquity. The Antiquity in which ‘miror’ was a verb denoting the action of looking and appreciating, and ‘speculum’ was the noun to betoken the thing in which one could see their image. The noun came from a verb meaning looking at something – without much the appreciative aspect.
Right, some say you see yourself in a mirror. I’m for the notion of an optical counterpart – I gotta have some attachment for myself as perceivable from within my very person. It could be also part my Theta Criterion. The argument might be just not overtly present. 
The human has obviously changed much since the times of the caves and hardly anyone would ‘go ape’ over a piece of a mirror nowadays. Asking ‘Is this you’, pointing at a photograph, would stand for ‘Is this a photograph of your person’ – a fact easy to tell should there be an intention to place anyone next to a portion of cash.
Mirrors provide images reflecting anything visible – a painting or a photograph will remain static in its giving a picture. Metaphors like ‘a mirror of your soul’ might take from this very general regularity to concern mirrors and visible objects. These could be only very general aspects of use to occasion the mirror metaphor about language – and mirrors have been associated with vanity! 
Theta roles could relate to such general tenets about language. All languages have nouns and verbs. Those nouns and verbs coact in utterances. Generative grammar labels these interactions theta roles or thematic relations. The term ‘theta roles’ has nothing in common with the theta brain wavelength (feel welcome to see ‘The scientific theta’, my another post).
The interesting part about the vain mirror is the change that the use of the lexical items has undergone over the centuries. The object as nowadays, the mirror, takes its name from the Latin verb correlating to admiration. The ancient object, ‘speculum’, derived from the action of just looking and seeing. This would be however the looking-glass to connote self-admiration to a contemporary editor!
‘Mirrors are commonly used for personal grooming or admiring oneself (in which case the archaic term looking-glass is sometimes still used)’, as you’re welcome to see in Wikipedia. Hopefully, this is not the syntactically more elaborate form of the looking-glass when compared to simply a mirror (a single lexical item) to bring up the association with excess self-care. Syntax would be definitely an indispensable vanity.
The ‘looking glass’ has a theta role about it. A looking glass is the glass you look into – not a glass to look at yourself. Like ‘running shoes’ and ‘swimming suits’, it clips a verb phrase into a gerundive. All languages have syntaxes. Syntax could be termed the wonder and the mirror of the mind. Should there be associations to narcissism, some self-adoration is going to remain absolutely necessary.
For an option to chase your shoes successfully, feel welcome to see ‘Datta lie?’ – my next post.
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