• "I" as the writer alone, speaking out of personal experience to illustrate, usually, some personal opinion ("The idea is particularly useful. I, for example, have . . . ").
• "I" as a representative of or spokesperson for a group, often used after formal, rhetorical questions ("What does this country and this party need?"  "I suggest . . . , "  "I answer . . . ,"  "I declare . . . ").
• "I" as a hypothetical substitute for "one" ("When I refuse to obey an unjust law, I do not contest the right of the majority to command":  Alexis de Tocqueville, Democracy in America).
• "I" as an impersonal guide in formal exposition or argument, used to retard a quick line of thought ("This idea is in theory simple, I submit, but in practice, difficult")  --  sometimes to order a long, complex logical/rhetorical form ("I have explicitly argued that . . . ," "I have earlier suggested that . . . ").

Uses of "We"

• "We" as a familiar rhetorical agent including the writer and reader ("We must, of course, both agree").
• "We" as a spokesperson for a group, "the editorial we" ("We endorse the [Daily World's, Newsweek's, Rolling Stone's] view").
• "We" as a representative of a group -- possibly excluding the reader's ("We Harborites," "We Americans," "We Christians").
• "We" as all humankind ("We're all doomed").

Uses of "One"

• "One" as representing either the writer or reader ("Understanding as much, one should see that . . .").
• "One" as a cleverly disguised "I," though used with an "I" for formal emphasis or variety ("I agree, of course, but one wonders if the 'ayes' could still have it").
• In British English: "One wonders when one is British if one is living one's life rather too formally?"

Uses of "You"

• "You" as one's individual reader in letters or in exposition in understood form ("Consider the notion that . . . , " "Take the case of . . . ," "Notice the implication that . . . ").
• "You" as a vague indefinite reference used together with "we" for informal, even ironic emphasis or variety   (T. S. Eliot, "Tradition and the Individual Talent":  "In English writing we seldom speak of tradition . . .  You can hardly make the word agreeable to English ears without . . . comfortable reference to the reassuring science of archaeology").