{Preface: If this is horribly confusing, ignore it. I'm writing my senior thesis in Japanese history & literature, which means I'm thinking a lot about different cultures of citation.)
In addition to what branchandroot said, which is probably the most important thing to think about for citing, it also depends on the "culture" of the particular field that you're writing in, which might be part of what makes it confusing.
For example, citing in law review articles is usually mandatory if you're saying anything that you want people to believe, regardless of whether you feel you've demonstrated it with your own examples in the text. You also can (and frequently should) put tangential arguments down in the footnotes, so that people willing to take you on faith can keep reading, while others can dig into your research.
In my experience with literary analysis, on the other hand, scholars seem to want more of the argument in the essay, as it were, than down in the footnotes, though the footnotes can point you to other scholars with other arguments. Depending upon your audience (are you writing for an audience that prefers close-reading or critical theory?), it will be more or less important to cite other people's *ideas* versus using specific quotations from source texts in the essay and citing those.
So, to take "white symbolizes purity", in three* different contexts: Law: White symbolizes purity (Footnote: As X, Y, Z have all argued in articles A, B, C. While G may disagree in article H, this is why X is actually correct.) Close-reading: White symbolizes purity in these other parts of the text "quote" (footnote: where from) "quote" (footnote) "quote" (footnote), so it's doing the same thing here. Critical Theory: As scholar X demonstrated when writing about Y, white symbolizes purity in this context. (footnote: scholar X, possibly with some elaboration on X's thought) *Obviously, good lit scholars use both the close-reading and critical theory styles, but those are extreme examples to give some idea of the differences.
History seems to fall somewhere between law and close-reading lit, and according to my friends, the sciences have their own culture. So, very long-winded way of saying it depends heavily on your audience, and depending upon the field you're writing/reading in, the expectations may be different. I generally go with the rule of thumb that I should cite any argument (find someone else who has already made it) unless I'm prepared to spend substantial time (at least a paragraph for short essays) proving it and also cite any facts that are more obscure than "the earth is round", but this has definitely led to me getting papers back from lit professors going, "good citations, but possibly an excessive number of them."
no subject
In addition to what branchandroot said, which is probably the most important thing to think about for citing, it also depends on the "culture" of the particular field that you're writing in, which might be part of what makes it confusing.
For example, citing in law review articles is usually mandatory if you're saying anything that you want people to believe, regardless of whether you feel you've demonstrated it with your own examples in the text. You also can (and frequently should) put tangential arguments down in the footnotes, so that people willing to take you on faith can keep reading, while others can dig into your research.
In my experience with literary analysis, on the other hand, scholars seem to want more of the argument in the essay, as it were, than down in the footnotes, though the footnotes can point you to other scholars with other arguments. Depending upon your audience (are you writing for an audience that prefers close-reading or critical theory?), it will be more or less important to cite other people's *ideas* versus using specific quotations from source texts in the essay and citing those.
So, to take "white symbolizes purity", in three* different contexts:
Law: White symbolizes purity (Footnote: As X, Y, Z have all argued in articles A, B, C. While G may disagree in article H, this is why X is actually correct.)
Close-reading: White symbolizes purity in these other parts of the text "quote" (footnote: where from) "quote" (footnote) "quote" (footnote), so it's doing the same thing here.
Critical Theory: As scholar X demonstrated when writing about Y, white symbolizes purity in this context. (footnote: scholar X, possibly with some elaboration on X's thought)
*Obviously, good lit scholars use both the close-reading and critical theory styles, but those are extreme examples to give some idea of the differences.
History seems to fall somewhere between law and close-reading lit, and according to my friends, the sciences have their own culture. So, very long-winded way of saying it depends heavily on your audience, and depending upon the field you're writing/reading in, the expectations may be different. I generally go with the rule of thumb that I should cite any argument (find someone else who has already made it) unless I'm prepared to spend substantial time (at least a paragraph for short essays) proving it and also cite any facts that are more obscure than "the earth is round", but this has definitely led to me getting papers back from lit professors going, "good citations, but possibly an excessive number of them."