On listening to the silence following a sound, we may register that the silence isn’t silent, but that it contains sounds – and we may conclude that silence, in a sense, doesn’t exist. Nonetheless a musician will handle silence (the pauses) in the music, regardless of noise, for example from the audience, that may fill the pauses (with sound we may call music) et cetera.
Word images may be inverted, so that the word comes across as white on black. We may question both blackness and whiteness. Black stick ink which is often used in Japanese or Chinese calligraphy, is often tinted one way or the other in the colour scheme; towards blue, or red etc. The same can apply to a black printing colour. Likewise white paper comes in all kinds of tinted whites; ivory, cream, blue-grey etc.
The typographer or calligrapher will handle this whiteness and blackness in the same manner that the musician handles pauses, tones, rhythms. Often visual modes of expression will be termed ‘quiet’ or ‘noisy’ –
as if silence and spaciousness share common ground.
Proportions of margins have been very diverse over the years, from relatively compact scrolls in Egyptian, Hebrew or Greek, to Medieval or Renaissance manu-scripts. Japanese, Chinese or Arabic margins have been handled differently, conditioned by differences in the writing systems themselves (like differing directions of writing and reading).
Publishers have argued that paper is costly, and that the page is filled to the brim with text for this reason. Animal skin, used as writing material for hundreds of years, in comparison, certainly wasn’t cheap either. One may suspect that the reason is a lack of awareness of and respect for emptiness or spaciousness, giving it a low status. There have been instances in which the space around a block of text has been treated as a space for contemplation. Are we able to treat spaciousness with more respect, and less like dead meat?
A principle of proximity is useful in working with letters. A letter which is closer to another letter creates a bond; several letters close to one another may form words. If a letter gets closer to another visual element, like the edge of the page, it will break away from this bond. Letters form words, words form sentences, sentences form blocks of text, blocks of text relate to one another, headings relate to blocks of text, sub-headings relate to both headings and blocks of text, foot notes to the blocks of text. Good typographic work will rely upon a sensible distribution of space.
If the distance between letters become larger than the distance between words, meaning is disturbed. 
If the distances between words become larger than the distance between the lines, the line looses much of its function, which is to help the eye in reading. 
If the distance between two blocks of text become smaller than the interlinear distance, the blocks of text loose their independence. 
If the distance between the heading and the first paragraph is smaller than the distance between the paragraphs, the heading will form an alliance with the first paragraph, removing its connection with the other paragraphs. 
In short: A typographic element will bond with the closest typographic element. This also applies to frames, lines, the edge of the page, ornaments and illustrations.
The space(s) between letters will also influence the shape of the letters themselves. Minuscules have a more even width than majuscules; minuscules are largely the same width, with a few exceptions: r and f will let in more space than most other minuscules, and a calligrapher will be tempted to adjust their width, or create ligatures. 
A type designer will have to plan for these problems in advance, through test and error, and will often make letters like r and f shorter than other minuscules, so that they let in less space, even though the letter itself may look less gracious. 
A type designer working digitally will be able to define the distances between combinations of letters (kerning pairs), so that the letters that cause an uneven texture due to uneven spacing, will behave better.
db may be too tightly spaced, and in the kerning tables (the digitally described spaces between letters) they may be moved further apart. r and i will look far apart, the type designer will move them closer to one another etc.
A badly designed font can use imported kerning tables from another font, with the result that letters will have random spaces applied to them, like a badly fit jacket.
A good digital font will therefore contain kerning values particular to that specific font that determine the space between the letters.
One of the most common misperceptions in regard to the spaces between letters is that the distances be-tween them should be measured from a letter’s extremity. This is a rigid and inflexible idea. Emily Dickinson is quoted as saying (in a play by William Luce): ‘I look at words as if they were entities, sacred beings’. We will benefit from looking at letters and words as if they were alive. For example: If you were to ask a group of people to stand in line and keep an arm’s length distance between one another, the spaces between them would end up different, as we have different lengths of arms.
Ideally the space(s) between letters should be optically the same. This is how you make sure the letters make up an even texture on the page. It might be useful to
squint at a text to see if certain combinations of letters need adjusting: Strokes that are too close to one another form denser clusters of black in the text.
The proportions of majuscules are more complicated than the minuscules. Their width often differ. If we aim for an equal amount of optical space between the letters, it makes sense to make E, F and L narrower, so they can be placed closer to the next letter, allowing for a more even distribution of space.They are open letters that let in a lot of space. P, R, B and S are narrow letters, primarily because this ensures a likeness in form to the ‘mother letter’ O. They repeat the form of the O, not its width..
Some typefaces will make optical spacing difficult: Helvetica, Franklin Gothic and other industrial sans serifs approach a similar letter width, which was a wide-spread misconception during the 1800s. The only way of resolving spacing issues with a wide capital letter L, which lets in a lot of space, is to kern (letterspace) the text loosely, and then individually tighten the loose combinations; LA, RA, TT etc. In addition to being time consuming, it will demand more interlinear space, and therefore make the design work more complex. 
First of all, capitals should be spaced loosely. It is easier to tighten the spacing between individual kerning pairs manually (locally) that way. Typical pairs are RA, LA, VY, OO, TT.  In principle, straight strokes following one another should be loosely kerned. Kerning tables are normally inadequate. Majuscules are peculiar and eclectic in nature, and they demand special treatment.
A place to start would be about 4/5 of the inner area of the letter H,  letting that be the ideal space between our majuscules. With this, it might be possible to create a system for calculating the distances between letters, like David Kindersley did. But majuscules can also be spaced looser. The most important thing with a looser letter fit would be to keep the interlinear distance larger than the spaces between words. Looser kerning demands looser word spaces which demands looser interlinear distance.
I will gladly leave the task of creating a system for calculating spacing between letters to others. I am content drawing up some general principles. For even if one managed to calculate the whole area between the letters and made it equal, one would fail. Optical spacing between letters is just that; optical. What a mathematical system of spacing will tell us is irrelevant, as long as it looks wrong to a trained eye. For example; the inner
corners of certain letters, typically F, L and E, are not to be counted as space between letters, but as space belonging to the letter. Perhaps we can say that it has a personal space, so that parts of the space around the letter escapes us, making a rigid system meaningless. If the letters have serifs, this will also affect the distances between letters. A majuscule E set in a sans serif versus an oldstyle font will illustrate the point.
It will be useful to sketch in the distance between letters to compare letter pairs. 
A far less common phenomenon is loosely spaced minuscules. The American type designer Fredric Goudy once received an award which was set in (too) loosely spaced gothic letters (Americans call them ‘blackletter’). His comment: ‘People who would letter space minuscules are people who would steal sheep’. This gave birth to the book title ‘Stop stealing sheep [and find out how type works]’. Robert Bringhurst mentions a derivation from this rule: Compressed (narrow) sans serifs can be spaced slightly loose in order to increase legibility. And sans serifs are often spaced too tightly, and can be spaced a little looser. [11,12]
A good basic rule for oldstyle minuscules is to let the areas between the letters be a little less than the internal areas of the letters themselves. As opposed to italic fonts, where the areas between the letters are almost the same.
The smaller the size of the letter is, the looser the kerning. The larger the letters, the tighter the kerning can be. Typographically these variables are baked into the kerning table, so that the smaller letters are (unnoticeably) kerned looser. Titling faces made for use in larger sizes are kerned tighter. In some fonts, like Optima Nova Titling, Mantinia and Waters Titling, there are even specially designed ligatures, that point to the written origin of the letters, and the scribe’s adaptability. 
Word spaces should be larger than letter spaces. Interlinear distance should be larger than the word spaces. The distance between heading and main text should be larger than the interlinear space. The distance between the heading and the edge of the page should be larger than the distance between heading and main text. 
A block of text that has the same amount of space top and bottom looks too low. In Hebrew and Egyptian scrolls the text was arranged in columns, and in principle they could be placed equidistantly. When the codex form came about by papyrus, then vellum, were folded and put in piles, and then sewn together to form primitive books, two columns were used, one for each page. After a while it became common practice to pull these together, so the gap between them was minimized. And the margin below the text was made larger than the margin above. Not only does this give the page a better poise, it also provides room for the fingers to hold the book without touching the inked letters on the page. Jan Tschichold researched Medieval and Renaissance manuscripts and discovered relationships between margins that created a unity between the blocks of text, the margins and the format of the book. Robert Bringhurst has taken Tschichold’s geometrical diagrams for book proportions even further.
Geometry is often insufficient in itself: If the portrait format of the book is in a Golden proportion in relation to width and height, for example ca. 21:34, it will look a little tall, and needs to be shortened slightly optically. If it is a landscape format, 34:21, it will look a little narrow, and will look better optically broadened. This adjustment needs to be solely an optical one, so the Golden proportion should only be a starting point. The same is the case with Tschichold’s placement of the text on the page. If slavishly followed, Tschichold’s simple basic grid will make the text area look as if it’s placed too high, and it will need to be optically moved downwards. Much of the inner margin in thicker books will disappear, so it will be a good idea to increase it. 
Rules, principles and geometry gives us a starting point and a basis to treat visual space. But they don’t guarantee a sensitivity or skill in relation to how we treat spaciousness. At best they point to what visual challenges and complexities that occur in dealing with letters, so random choices can be avoided. Regardless: The spaces in and between words, lines, groups of texts, pages of books are of at least as great importance as the letters, words and sentences in themselves, and indeed it makes no sense dealing with them as separate phenomena. We may poeticise and dream of the space between solar systems and atoms, but there are far more concrete and practical spaces that are awaiting our discovery.[