News that a US government intelligence body is going to start analysing the metaphors used in various languages will have brought wry smiles to the faces of writers and critics. Presumably, "Metaphor Program" agents won't restrict themselves to metaphors as that particular word is often used metonymically for the whole of figurative language – similes, symbols or indeed any use of language that appears to be standing in for something else or representing something else. That in itself is no simple matter, as we shall see, but let it stand for the moment.

"I wandered lonely as a cloud ..." to which we are entitled to ask, "What's lonely about a cloud?" It's a pretty rare Lake District sky that gives us one cloud on its own. But who says a lonely cloud would have to be on its own to be lonely? Maybe clouds are just lonely things – full of a sense of their isolation in an alienated world. If we find ourselves grasping at straws here, Wordsworth gives us help: "... that floats on high o'er vales and hills", which suggests that he's talking about the cloud's detachment from the earth. It's the higher-than-hills-ness, floatiness of the cloud that is important.

This is the kind of speculation that metaphor-divining specialises in and it's fun to think of US spooks chewing over such matters – though presumably they will hire patriotic literature graduates to do the job.

Such servants to the US cause will be able to take their masters on a trip through a forest of suggestion, resonance and ambiguity in their quest to find the hidden value-systems in speakers' and writers' use of metaphor. We now know that Wordsworth's idea of a writer being detached from the world, wrapped up in thoughts about nature and the imagination, was indeed ideological – as he warned us:

"The world is too much with us; late and soon,

Getting and spending, we lay waste our powers.

Little we see in Nature that is ours."



So, straight away, our US allies can label early Wordsworth an anti-bourgeois subversive – someone who will need to be watched.

But what of Shakespeare? He poses the problem that we can never know for certain that this is Shakespeare talking or one of his many characters through whom he speaks: "Whether 'tis nobler in the mind to suffer/The slings and arrows of outrageous fortune ..." This is dense stuff: a cast of thought has to compress our interactions and outcome into one notion: "fortune", which then has to be personified into a form that can "behave" or have appurtenances, as in this case "slings and arrows". Aha, militaristic metaphor! Fortune is armed and aggressive. Clearly, Hamlet is a potential terrorist. And indeed he was. Or tried rather ineffectually to be. But the writer who conjured him up? Probably not.

In that tiny section of Hamlet's soliloquy, is what we might call a hidden metaphor: "nobler". Linguists have noticed that across the history of language some words start out as obvious, conscious metaphors and then slowly embed themselves in our daily usage in such a way that we're no longer aware that they are metaphors. Some extrapolate that even further to suggest that virtually all language is metaphorical. Behaving "nobly" is wrapped up one way or another with the position of being a "noble" (a highly ideological view) but, over time, moves free of that attachment. The word "window" meant in its original Scandinavian, "wind-eye" – a figurative view of the hole in the side of a hut through which the wind blew in and a person could look out. Excavating the original meanings in the Old English, Latin and Greek origins to modern English words often brings up such lost metaphors. Will the spooks be looking this deeply? Probably not.

Glancing over the words I've used, you will see many metaphors and some hidden: "further", "deeply" "daily". We often use space-and-time words with little regard for whether we really mean it. If I say, "far be it for me to ..." there isn't anything "far" about it. I don't really mean "daily usage". The word "day" has been enlisted by our metaphorising brains to mean anything regular or continuous. Working harder to understand something really doesn't take me anywhere "deeper'. Perhaps the spooks would spot in me here a dangerous attitude to the truth: someone who has rejected the principles of empirically proven knowledge.

And what of grammar? Can that be metaphorical? In Germanic languages we use the word "have" semantically to mean "possess" and grammatically to signify the past: "I have eaten ..." "Aha," cries our US agent, "bourgeois acquisitiveness is embedded metaphorically at a sub-conscious level even into our understanding of how time passes. Good. Greed is good. Good."

Those of us of a certain age were inducted into this discourse with an inspiring, frustrating book, William Empson's Seven Types of Ambiguity. The ever more windingly we wandered around Andrew Marvell's garden, the more some of us realised we were in fact wandering around Empson's mind. And this will be the spooks' main problem. The more they pin down and describe a metaphor, the more they will find that they have pinned down and described themselves.