If you’d like to buy a copy of Newton’s Opticks: or, A Treatise of the Reflexions, Refractions, Inflexions and Colours of Light, published in 1704, there’s one on AbeBooks for £131,245.03, plus £12 P&P. Do people just click on such items, I wonder, and wait for the book to plop through the letterbox a few days later?

Anyway, there is a meaning of optics now being heavily used that Newton wouldn’t have understood. It is not the first time this has happened, because, for pub-going folk, optics are the measures attached to upside-down bottle of spirits to dispense reliably mean doses. Optic in this sense began as a trade name and has been in use only since 1926.

Newton did not invent the term optics for the science of visible light. It had been brought into English from Latin in 1579 by Leonard Digges (not to be confused with his grandson Leonard, the translator of the nicely titled romance Gerardo, the Unfortunate Spaniard). Optics was originally regarded as plural in English, since it derived from the plural Greek word optika, ‘optical matters’. But optics has been construed as singular since the 19th century.

The overused new sense of optics is most commonly found in political contexts, for it simply means ‘appearances’, which are professional life or death for politicians. ‘The optics were important for Turnbull,’ explained a piece in the Guardian on Australian politics, ‘Addressing the nation with Scott Morrison and Mathias Cormann by his side sent a strong message to his internal foes.’ It’s all to do with what people perceive (a word that has acquired a connotation of mistaken perception).

Oddly enough appearances long ago found a place in the theories of astronomy, in which optics played such an important part. To save (or, earlier, salve) the appearances meant ‘to accommodate a hypothesis to observations’, such as the movement of planets.

The earlier form of the phrase was save the phenomena, transferring the Greek word directly into English. But in parallel (as in John Florio’s translation of Montaigne), save appearances also bore the sense of keeping them up, like Hyacinth Bucket. Optics meant a lot to her.