I liked Vivian Gornick on the difference between talking to someone on the phone and writing a letter:

‘When we talk we each cradle the receiver, stare unseeing into the emptiness of the rooms we occupy, and concentrate on the exchange … The telephone conversation is, by its very nature, reactive not reflective. Immediacy is its prime virtue. The immediacy delivers quick company, instant stimulation; the stimulation is cathartic; catharsis pushes back anxiety; into open space flows the kind of thought generated by electric return. The letter, written in absorbed solitude, is an act of faith; it assumes the presence of humanity; world and self are generated from within; loneliness is courted not feared. To write a letter is to be alone with my thoughts in the conjured presence of another person. I keep myself imaginative company. I occupy the empty room. I alone infuse the silence.’

(From Approaching Eye Level (1997), pp. 152, 162)