
Paulette L. answered 04/13/19
Experienced, Patient, English Language Tutor for Adults
Commonly, the pronoun "on" ("one") is used in place of "we", when it applies generally as in this case: "We know everything", so it would be "on sait tout". Here, "everything" is non-countable, and when gender isn't known or doesn't matter, the masculine "tout" is applied. So, "tout le monde" ("all the world" or, more commonly, "everyone") because "monde" isn't countable and the "t" isn't pronounced (because it never is unless it's followed by an "e"; but "toutes les femmes" (all the women) refers to all the (countable noun, plural, feminine, "t" is pronounced because it's followed by an "e", but the "s"at end not pronounced). "Tous les hommes" ("all the men"= countable, "all", masculine, plural, "s" not pronounced. But in "Bonjours, tous" ("hello, everyone"), "tous" is a pronoun, not an adjective, and the "s" at the end IS pronounced.