‘Mind-forged manacles’, as well as being one of Blake’s most resonant phrases, also shows how well (and succinctly) poetry (and art in general) can express a complex idea that it is difficult to express by standard reasoning.

At the heart of Blake’s phrase is a contradiction, something that is anathema to conventional reason: ‘forging’ is the working of metal by force and, generally, heat; ‘manacles’ are metal shackles used for physical restraint; yet ‘mind’ is immaterial; mental, not physical.

It is precisely in that contradiction that the power of Blake’s metaphor resides: he wants to emphasise the simultaneous strength and weakness of convention, man-made rules, which can bind us as strongly as steel shackles yet are self-imposed and entirely insubstantial – they are discarded not by physical strength but an effort of will, through recognising them for what they are (though that recognition is not enough in itself: it takes a conscious effort of will to break conventions).

(It is important to understand that by ‘convention’ I mean rather more than the trivial, like dressing or speaking in a particular way; I mean the whole vast hinterland of ‘agreed ways of thinking about things’)

The power of the mind is, I  think, generally underestimated and misunderstood, largely because we equate ‘power’ with physical force – so that proof of ‘mental power’ would be something like telekinesis, moving objects at a distance simply by thinking about it.That in turn stems from a narrow view of the world itself, which supposes it to consist only of what is physical: that is the ‘real world’ in which we are so often told we must live – yet the reality is quite the opposite.

Our world consists, to a very great degree, of mental constructs – it is, in other words, mind-forged. Our way of perceiving the world is an ingrained habit of thought more than anything: it is not simply a matter of opening our senses and letting the outside world flood in; our interaction with our surroundings is a continuous act of interpretation, along lines that have largely become instinctive; but as various ingenious experiments show, our minds can be deceived.

For instance, if we watch a mouth making a ‘b’ sound (technically termed a labial plosive: the lips are pressed together then blown apart) then see instead the mouth making a ‘v’ sound (a labio-dental fricative, where the lower lip is first caught behind the top teeth) we will hear a ‘v’ sound, even if the actual sound remains the same; and if the image switches back to the appropriate lip formation, we will hear the sound as a ‘b’ again; this will happen invariably – as long as we attend to the visual cue, it will override and alter the information our ears give us. This is called the McGurk effect – you can try it yourself here.

This also shows how important faces are to us, and how minutely we examine them for information – so it is no surprise that we have the knack of seeing them in chance arrangements (pareidolia is the term, I believe) and also that we interpret things such as cars (with headlights like eyes and radiator-grilles like mouths) as having ‘faces’ (some amusing instances here). We can play with this tendency too: if we take the inverse mould of a face (such as the inside of a mask) we tend to see it as a positive face, which leads to weird effects if it is rotated – we continue to interpret the image as positive, and this causes us to see the rotation happening in the opposite direction to the actual movement (illustrated here).

This is something that has long troubled philosophers – in essence, it is the same thing as the bent stick in water that exercised Plato: what we see (that the stick appears bent where it enters the water) is contradicted by what we know (that the stick is actually straight). This led Plato – and all who followed him – down the path of distrusting the senses, and maintaining a distinction between Appearance (deemed to be deceptive) and Reality (capable of being apprehended only by the intellect). Having spent much of my adult life in thrall to Plato, I now consider that a wrong direction, as I discussed elsewhere.

To be fair, my repudiation of Plato is as much about a change in my own temperament as anything else: when we are young, we are eager that mysteries should be solved; where there is doubt, we yearn for certainty. Now, in age, I find the mystery itself exciting and engagement with it more satisfying than any solution; the one thing sure about certainty is that it is not to be relied on – the best it can offer is a temporary reassurance which allows us to turn to other things. But the real pleasure lies in engagement: as Eliot puts it,

‘For us, there is only the trying. The rest is not our business.’

I used to find it distressing that, shortly before his death, Thomas Aquinas – one of the most formidable intellects of his (or any other) age, a man who thought hard about God all his life and wrote deeply on the matter – had a vision that prompted him to say “All that I have written appears to be as so much straw after the things that have been revealed to me.” Now, I find that reassuring, and it reminds me of Wittgenstein, at the end of the Tractatus:

‘6.54 My propositions are elucidatory in this way: he who understands
me finally recognizes them as senseless, when he has climbed out
through them, on them, over them. (He must so to speak throw
away the ladder, after he has climbed up on it.)
He must surmount these propositions; then he sees the world
rightly.

7 Whereof one cannot speak, thereof one must be silent.’

Wittgenstein got that right, I think: language is not the best medium for engaging with the mystery, at least not the language of philosophy and rational discourse; poetry will get you closer – like the Blake quotation we started with, or Eliot’s Four Quartets – though my own instinct is that music or art are better tools of expression; but ultimately, perhaps, it is silent contemplation that will bring us closest to understanding.