Yet an extraordinary case reported shows us that there may be another form of miracle that can help the blind to 'see' - and it's one that may force us to rethink our whole understanding of the way in which the human senses operate.
In the journal Current Biology it is reported that a man left totally blind by brain damage has astounded scientists by flawlessly navigating an obstacle course without any help or practice whatsoever.
This is perhaps the most persuasive example to date of what is termed 'blindsight' - the extraordinary ability of some who have lost their vision to be able to 'see' without, apparently, any ability actually to receive images in the eye and brain at all.
Because blindsight is a nebulous concept, often linked to paranormal manifestations, it has often been dismissed by researchers as myth. Yet here was a case that defied any straightforward explanation.
Scientists at the University of Tilburg in The Netherlands found that the unnamed man, known only as 'TN', was able to negotiate his way past a series of boxes and chairs, despite the fact that a series of strokes had damaged the visual cortex of his brain to such an extent that tests have shown he is completely blind.
So how on earth does he do it? What does it tell us about the way we 'see' the world?
And is it conclusive proof, as many have claimed, that humans have a hidden 'sixth sense' that can detect aspects of the world around us in a way that defies any logical explanation?
The first thing to realise is that science loves to categorise things.
We have 'five senses' in part because 'five-and-a-bit senses' is messy and ' unscientific'.
And yet it may be a far more accurate description of what is going on in the complex interface between the outside world and our brains.
It seems that in the case of TN, for example, although he has no conscious awareness of the visual world, his brain is, somehow, keeping tabs on his surroundings, by processing the electrical messages that are travelling through his eyes and optic nerves (which remain undamaged by his stroke) even though the normal 'visual' part of his brain is damaged beyond repair.
To use a scientific term, his mind is not creating any visual 'qualia' - the name given to conscious experience of sensations, such as sight or sound.
Although he is not actually aware of the cause, scans have even revealed that certain parts of his brain, not normally associated with sight, 'light up' when he is shown pictures of other people pulling a variety of different facial expressions - such as fear, anger or joy.
This weirdness should perhaps not surprise us. Our senses form part of the most mysterious system in the known universe - the human brain.
Indeed, compared to the kilogram of grey jelly in your skull, even the mightiest stars and galaxies hold few mysteries.
Anyone who claims they know how the brain works, or exactly what is going on when our eyes view a splash of red, or our noses scent a whiff of coffee, or our tastebuds pick up on a tang of brine, is simply deluded or lying.
Despite centuries of probing, such mysteries remain totally unsolved.
We do know, however, that there are a number of peculiar anomalies.
For example, we know that humans, compared to other animals, have extremely good vision - on a par with the birds and far better than most mammals. Sight is our primary sense.
Yet, rather mysteriously, it is another sense - smell - which in many of us has the ability to evoke the strongest emotional responses.
Shown a photograph of our old primary school, say, most of us will respond with a vague sense of recognition.
In contrast, even the merest hint of the smell of the school's polished parquet floors, or of the heady tang of boiled cabbage from the school dinner kitchens, will be enough to bring all the childhood memories flooding back.
Equally mysteriously, our senses seem to operate on several levels. If you are sitting down when you read this article, think for a moment of the sensation coming from your bottom and lower back.
The moment you do, you will become suddenly aware of the pressure of the seat cushion below you, the contours of its shape and how comfortable (or uncomfortable) it is.
In psychological terms, you are now 'attending' to these sensory inputs.
Yet before you chose to swivel your 'mind's eye' to the chair, you were probably completely unconscious of all these sensations, even though the relevant one of the your five senses - touch - was working all the while.
Then there is a well-known psychological phenomenon called the 'cocktail party effect'.
This is the ability of the human brain to detect, immediately, pertinent and important information from an otherwise meaningless sensory melange.
If you are at a busy party, for instance, you will probably be aware only of the random babble and hum of voices. Yet should someone mention your name, even quietly and from across the room, the chances are that you will immediately pick up on it.
It is as though you have an unconscious monitor sitting inside your head - a 'little man', if you will - checking what is coming in from your eyes and ears and so forth, before deciding which is important-and letting your conscious mind know.
Of course, the idea of a little man inside your head is an absurd (but remarkably persistent) analogy - but it does serve to illustrate the fact that our brains operate on all sorts of levels of conscious awareness, and not always in ways that we recognise.
Think of the last time you drove to work, for instance, or did the school run. How conscious were you, actually, of the journey? How many of the twists and turns can you remember?
The chances are that the answer is 'none at all'; you probably were able to operate, quite safely, a complex piece of machinery (a car) almost like you were an unthinking robot while you were thinking about something more interesting. Extraordinary.
The interaction between the 'mind' and the senses really is one of the most amazing aspects of the natural world.
And since we cannot be sure how it works, it does seem foolish to dismiss, out of hand, 'sixth sense' phenomena such as blindsight.
It is probably even the case that we should not rush to dismiss, completely out of hand, even stranger 'paranormal' mental powers, such as telepathy, even though hard scientific evidence is lacking for such things.
The only certainty is that the more we learn about the workings of the mind, the more fantastical its abilities are proving to be.