Newton’s theory of the spectrum, swearing Neopolitans, the education of the deaf: Victoria Neumark finds it all in this book about the voice

How many colours are there in the rainbow? You, I and every schoolchild knows that there are seven: red, orange, yellow, green, blue, indigo and violet.

Or we think we know that. Yes, there is a range of colour, in a fixed order, with hues that we could pick out. But where does one begin and another end? Is that violet or purple? Where does red shade into orange? Is that, actually, indigo? And, of course, secondary pupils know about ultraviolet and infrared. So where do the seven colours come from?

In 1669, the young Isaac Newton was beginning his lifelong fascination with the idea that “harmonies of colours” might be “analogous to the concordances of sounds”. He noticed that diffracting colours through a prism produced the same invariant order as sunlight diffracted through rain. He called this structure the shadow or phantom of sunlight - its ghost or spectre (spectrum in Latin). He noted the colours red, yellow, green, blue and violet.

But because Newton, like many philosophers, wanted a giant, inclusive scheme for understanding the universe, he, “revised his perceptions,” says Jonathan Ree, to include the then slang words of “orange” (a rare fruit in the mid-17th century) and “indigo” (a dye or ink). He did so because he wanted there to be seven colours in nature as there were seven tones in the octave of ancient Greek and early Christian music, because he wanted to clinch the analogy between colours and sounds.

And thus, not only the scientific apparatus of a colour spectrum but also our everyday mental furniture of the rainbow spring from the rarefied obsessions of a thinker three centuries dead.

Such a story, dazzling in its implications, entrancing in itself, is just one of many which sizzle through Jonathan Ree’s exploration of the history of the voice in European thought.

Its overall project, to examine the cultural value placed on the voice, as expression of the human spirit, as carrier of language, as individual means of social exchange, is mediated through a careful history of the growth of education for deaf people. In this way, Ree roots all his theorising in personalities and situations - from the 18th-century academies of Scotland to the basic gestural swearing of 19th-century Neapolitans.

He divides his subject into three: histories of the metaphysics; the science; and the philosophy of the senses.

At the end, as well as knowing a lot more about the history of education for the deaf, the reader will have some grasp of why sign language is a real language, of how Dickens used to mark up his texts to give his extraordinary readings, of how historical etymology began. But more than this, the book transmits the intoxicating fever of philosophy, of wondering why along with everyone else who has wondered why. Look at that rainbow, for instance.